I found that the Skunk2 exhaust hangers above the muffler were too long and were rattling against the body of the car, being both annoying, and eventually leading to an exposed piece of metal to rust up on me.
What you'll need:
Jack, Ratcheting Jack Stands, Chocks (all the standard stuff, you should know the deal with this before attempting anything below)
14mm wrench, 14mm ratchet, Angle Grinder, a towel to rest the muffler on. Oh, and safety glasses.
1. Jack the car up using all the appropriate precautions
2. Take the muffler off
3. Set it down on a towel, make sure that the towel is only directly underneath the exhaust and there is no extra bit sticking out from underneath - sparks are going to fly like crazy here. (note - put your safety glasses on)
4. Measure about 1" from the end of the hangers and mark them.
5. Take a deep breath then start the angle grinder... with great care, slowly ease it onto the spot you've just marked on the hanger and begin to put pressure down onto the hanger. You'll start to carve out a notch, and you're just going to cut through the entire width of the hanger. As you get close to cutting through, apply minimal pressure, and take care not to touch any portion of the muffler with the grinding disc. Take a few extra moments and you'll get that last portion off. Use the grinder to smooth the edges a bit. Enjoy the orange glow from the near molten metal that is the exhaust hanger.
Note: The hanger and the bit you just cut off are extremely hot at this point - do not even think about touching these for at least 10-15 minutes afterwards.
6. Reinstall the muffler, inspect for clearance.
Here are some pics.
The issue:
Pre fix:
Post fix:
Reinstalled (note the damage on the body from the longer hangers rubbing against it:
I'm definitely going to make Skunk2 aware of this so they can shorten the length of the exhaust hangers a bit (ticket #2540). This would be something I'd recommend people just getting this exhaust do before installing it on their Si for the first time.