This document attempts to explain how to install a GHL exhaust on a standard 996 Carrera with chromed exhaust tips. Thanks to Erez Wolf (erezwolf@cybercom-intl.com) who installed a Fabspeed  for the pointers.
The usual disclaimers apply, I do not guarantee any of this and you are on your own when you do it. Also, remember that exhausts and cats get hot when the engine is running so make sure that all parts are nice and cold before you start!

GHL Exhaust as they come out of the box:

Tools needed for the exhaust:
Ramps or anything that jacks the car and allows you to work safely under it
Drive (ratchet)
13 mm socket
17 mm deep socket
13 mm wrench
WD 40

Tools needed for the tips:
Drive (ratchet)
17 mm deep socket (I really mean deep)
Big standard flat screw driver
Pliers
WD40
 

Time:
Being really relaxed and not trying to go fast at all, it took me precisely 3 hours to do the install, including taking pictures, going in the house to grab the scale, weighing both exhausts, etc. I believe that anyone with the right tools and a good understanding of what needs to happen can do this in an hour or less.

Instructions:
Spray the 2 17mm nuts that are on the clamp connecting the back of the cat to the exhaust and then loosen them up. Do not remove the bracket; just loosen it up. This will allow you to push it about 2 inches towards the cat.
You should now be able to see a gap between the collar and the exhaust

Locate the 3 13mm nuts that hold the exhaust to the car bracket. Spray some WD 40 on them and use the 13mm socket to remove them

To assist you with the 3 nuts, here is a view of the bracket on which they are connected. As you can see they are pretty close to one another.

You should now be able to rotate the muffler under and out of the car. You then remove the 2 large nuts and bolts that connect the bracket shown above to the factory exhaust (2 13mm nuts and 2 very long bolts) and place it on the GHL.

You can see me here doing it the hard way (under the car) instead of the smart way at ease muffler taken out….

This is what the exhausts look like when put next to one another

For those interested, the factory weighs 21.5 pounds and the GHL 14 pounds.

We now need to remove the tip from the factory exhaust and put it on the GHL.

To do this, you will have to loosen up a 17mm nut that requires a very deep socket because of the length of the bolt. Once the collar is open, you need to remove it from the factory exhaust and put it on the GHL. I used a big screw driver and pliers to pry it open and put it on the new exhaust. Here is a view of the parts of the collar on the factory exhaust and on the ground

The part on the factory exhaust

The whole thing disassembled

Ok, so now you put the big bracket as well as the tip on the GHL and reinstall the whole thing. There is a lot of room for adjustment for the tip so I just tightened the tip bracket enough for it not to fall off and started really tightening only when the muffler was on the car at the right spot and fully tightened. This way, I managed to get just the look I wanted for the tip: not too close to the bumper (melt problem…) and not too far to not have too wide a gap.

Picture of bracket and tip on the GHL

Repeat for the other side and enjoy the sound of Porsche as it should have been in the first place! I have to say that I thought they would be a little louder but all in all it’s a pretty good sound at a pretty decent volume, specially over 4000 RPM or when picking up from 2000RPM in a high gear.