The retrofit of the Porsche Litronic headlights is a substantial improvement of headlight performance.  I had previously driven with the new technology Xenon headlights and found them to be a great improvement over the standard Halogen headlights.  The lens shape must have also been redesigned as the beam shape is greatly changed and improved.  With the Litronic headlights the beam pattern is much wider, yet I have not received any flashing complaints from oncoming drivers.

Upon receipt of your retrofit kit unpack it and check the contents carefully.  The headlights are specific to each side of the Carrera.  There must be a connector receptacle on the outboard side of each headlight assembly, as there are left and right hand assemblies.  

Warning Label decals
Cable Adapter
Control Unit Plastic Bracket
Control Unit Base Bracket
Control Unit
Pop-rivet Nut
Pop-rivet 4 mm (2 per side)
Bolt M6 x 16
Torx Self Tapping Bolts (3 per side)
You should find 2 of each of the above.  

You will also want some black electrical tape, black RTV sealer, and di-electric lubricant.

If you do not have a Pop-Rivet Nut pull gun, you can purchase one from an automotive supply store.  HeliCoil makes one, but it does not have a 6 mm tread nosepiece, so I used ¼-20 rivet nuts and bolts.  One could also stop by his local shop and after having removed the two black plugs from the rivet nut holes hand some cash to a mechanic to go out and install the two pop-rivet nuts from the kit.  The pop-rivet nut allows the Control Unit bracket to be installed and removed without removing the headlight assembly, thus I would install the pop-rivet nuts even if I had to hold the nut with vise-grips and tighten a bolt into it until it is swaged into the hole.  Be careful as one could twist off the kit M6 bolt; get a high grade M6 from say a Caterpillar dealer.  Most DIY mechanics have a pop rivet gun, but it would also be possible to use a through bolt and nut to attach the base bracket.  

1. Open the trunk and get your lug nut lock key.
2. Remove the carpet from the trunk area.
3. Disconnect the Negative Cable from the Battery and place well away from the Battery post. 
4. Check #22 and #23 fuse locations within the Fuse Box.  Remove these two fuses.  If there are 7.5 Amp fuses here, you will need two 15 
Amp fuses.  If you have 15 Amp fuses you will be reinstalling them later.  
5. Loosen and remove the two Locking Lug Nuts from the front wheels.  I remove these Locking Lugs first and place them so that I will see them when finished so that I always remember to re-torque that wheel’s lug nuts.
6. Loosen, but do not remove the lug nuts for both front wheels.
7. Refer to the DIY section about jacking your Carrera and raise the two front wheels.
8. For now remove the Right Front Wheel.
9. Remove the Phillips head screws for Inner Fender Liner and pull front lower edge back out of Bumper Cover and then pull Inner Fender Liner down to remove.
10. Remove Right Hand Headlight assembly, same procedure as published in your owner’s manual.  Push locking lever down slightly and unclip locking lever from lock.  Rotate Locking Lever to aft position, headlight assembly should move forward and up.  Grasp headlight assembly and rotate Locking Lever to vertical position, pull headlight assembly forward up and out of headlight well.  Care must be exercised during this procedure so that paint finish is not damaged.  
11. Remove the rubber plug from the hole, aft of headlight aiming screw access cover.  Easiest to remove by pushing from backside while pulling flange of plug.  If you do not have this plugged hole, the Porsche Tech Bulletin states to use the Control Unit and its brackets to locate them.
12. Pull the Pop-rivet nut into the hole of plug removed in step 11 above.
13. Install the metal horseshoe shaped Control Unit Base Bracket. This bracket uses the two holes located below the rubber-plugged hole from steps 11 and 12; mine had small dots of masking tape covering them.  
14. Wrap vinyl electrical tape round and over the end of the Cable Adapter sleeving and down over the ends of the new contact pins.  
15. Remove the Wire Harness Grommet from the hole passing from the trunk into the headlight well.
16. Feed the taped end of the Cable Adapter through the Wire Harness Grommet.  Pass enough cable through the grommet to allow the Cable Adapter to be routed along with the existing headlight wire harness.
17. Use needle nose pliers to pinch the ends of the Blue Headlight Wire Harness Clamp together.  Once the ends are slightly compressed a slight push of the pliers and the clamp is removed from the bracket.  I removed two blue clamps to allow my headlight connector to extend down and out of the wheel well area.  Be careful with these clamps, as you will be reinstalling them.
18. Remove the Semi-clear Silicone Headlight Connector Vent Tube from the connector.
19. Remove Headlight Connector by rotating the bottom edge of connector to the inside and then, with connector at 90 degrees to the installed position, the locking key will fit through the slot.  Be sure to look on both sides of connector to see this square locking lug.  Extend existing headlight connector and wiring harness down and outside of wheel well.
20. I used an “O” ring extraction tool or pick to work on my headlight connector.
21. Take a close look at the connector pins on the new Cable Adapter.  When you grasp the wire you will see how the pins have two barbs that are simple tabs bent out from the pin barrel.  You are using the straight end of the “O” ring tool to push down these two barbs from the front side of the connector.  Connectors mate face-to-face.
22. Use the hooked end of the “O” ring extraction tool to click the Orange Lock Tabs to the outboard position.
23. Start with #1 position, this should be a Yellow or Yellow with Black striped wire.  Slide the straight end of the extraction tool into the connector from the front side.  Be sure to do both sides of the connector pin to get both barbs pressed down.  With the connector in your left hand grasp the wire with your right hand fingers and pull on the wire, It should only take a slight tug as at this point there should be nothing locking the pin into the connector.  
24. Next do the same for the Brown wire in connector position #2.  Starting with #1 and #2 gives you a chance to practice; because when you do #4 you must be careful as you will be reinstalling this connector pin.
25. Turn the connector around to the backside.  Use the “O” ring tool to remove the White Silicone Plugs from connector positions #6 and #9.  Try to keep at least one of these plugs to reinstall into the #4 position.
26. If you have removed #1 and #2 successfully then you are ready to perform the same task on the other Brown wire in connector position #4.  Be careful removing #4 as you will use the extraction tool to lift the locking barb tabs out into position, like the new connector pins, once it has been removed from the connector.  Once the barbs are out into their original position you may install this wire into the connector, at connector location #6 from the backside.  Be sure that the slot in the mating end of the pin is vertical when sliding the pin into the connector; the two locking barbs should be to either side of the pin.  I used a set of needle nose pliers that have a very small end to push the wire down into the connector and I could hear an audible click when the lock tabs went home.  A slight tug on the wire confirms that the wire has indeed locked into position.
27. Reinstall one of your White Silicone Plugs from connector positions #6 and #9 into the old #4 position.
28. Using black electrical tape, tape the ends of the existing headlight wiring harness and the new Cable Adapter together so that they are in line and parallel.
29. Cut the old connector pin from the Brown wire removed from connector pin #2.  Place a 2 inch long piece of heat shrink tube onto the end of the Brown wire.  Use heat to shrink the tube.  Now apply enough heat to the heat shrink to ignite the end of the tube.  Use pliers to pinch the end of the heat shrink closed. 
30. Install the new Brown wire into connector position #2.
31. Install the new White wire into connector position #1.
32. Install the new Larger Brown wire into connector position #9.
33. Slide the Orange Lock Tabs back to their inside or center position to lock the connector pins into the connector.
34. Strip enough insulation from the existing Yellow, or Yellow with stripe wire as well as the new Yellow with stripe wire from the Cable Adapter.  I then soldered the ends of these wires together as I am fully confident about solder connections, but I do not trust automotive crimp connections.  Headlights are safety items, like brakes, the tools used to crimp connections for automotive use do not apply enough force.  After soldering the Yellow wires I applied another 2 inch long piece of heat shrink tubing, again pinching the end together to seal it.  
35. Fold the Brown heat shrank wire and the two Yellow soldered and heat shrank wires backward and tape them down to the wiring harness.
36. Tape the existing harness and the new Cable Adapter together so that they run parallel, use wire ties to clamp the Cable Adapter along its run back to the Seal Grommet.
37. Install the two Blue clamps onto the two built up harnesses and route the headlight connector back to its position.
38. Reinstall the Headlight Connector into its bracket by inserting the square lug into the hole in the bracket and rotating the connector down and snapping it into position.
39. I used some di-electric lubricant to ward off any possible corrosion in the headlight connector.
40. Now I bet you think you are in trouble because you did not install the Black Plastic Control Unit Bracket onto the Cable Adapter before you routed and connected it.  Do not worry the Plastic Bracket is made so that you can install it over the Control Unit connector plug.  
41. Install the Control Unit connector into the Control Unit; it will only go one way, look for the slot on the connector and the tab inside of the Control Unit.  Install the Black Plastic Control Unit Bracket using the 3 screws supplied in the kit.  If your kit is short these screws, as mine was, I installed 5 mm x 10 mm, .80 thread pitch pan head screws, after I tapped threads into the Control Units.  Cutting threads into the Control Unit case eliminated the fear of stripping the head of the Torx bolts as they try to self-thread into the case.
42. Inside the trunk route the Cable adapter along with the existing wiring and install wire ties to secure.
43. Install tie wraps so that the Cable adapter has a nice 3 to 5 inch radius loop from the Control Unit to the existing wiring harnesses.
44. Slide the Black Plastic Control Unit Bracket with the mounted Control Unit down into the horseshoe shaped Base Bracket.  Install the bolt through the top flange hole of the Plastic Control Unit Bracket.
45. Clean surface of Control Unit with Rubbing Alcohol and install the High Voltage Warning Sticker.
46. Install the Right Hand Headlight Assembly; it is the one with the connector receptacle on the outboard side.
47. Reinstall the Inner Wheel Well Liner and Right Hand Front Wheel.

The left hand headlight installation is similar to the Right, except with the Windshield Washer Tank in place, the headlight connector must be reworked by pulling it through the left hand headlight opening.
1. Remove the Left Hand Headlight Assembly; the procedure is the same as for the Right.
2. Place a fender cover or several towels around the front of the headlight well.
3. Use needle nose pliers to remove the Blue clamp at the top of the headlight well.
4. Remove the Headlight Connector by rotating the bottom of the connector inboard or in a clockwise direction.
5. Pull the Headlight Connector through the headlight opening.  Use electrical tape to secure the loose connector and harness up to the top of the headlight opening.  You may want to insert rags into any openings into the headlight well area; in case you drop something then you will not have to remove the Left Front Wheel and Inner Wheel Well Liner.
6. Rework the Left Headlight Connector as you did the Right Headlight Connector.