Here is the post that I made of cutting mine down but mine was stock. Before i done mine though all I could find was people cutting down aftermarket exhaust's. so there shouldnt be a prob. finding the info just do a google search it was so simple to do mine and I believe after market is even easier becaus most of them the pipe runs straight threw instead of going all over the place like the stock exhaust...
To Shorten the Can:
Using a chop saw with a metal cutting blade
Drill out the rivets of the end cap and set that a side, measer 8 inches back and mark it
Go to the chop saw and get it all level, make sure you got some kind of eye protection cause sparks are all crazy and cool looking
Cut the pipe and if you cut far enough back you should have cut the end baffle out which is a series of pipes that direct the exhaust all over and weighs approx 7-10 lbs
Bend the inner pipe up that comes out of the middle baffle to line up more with the end cap
Slip the end cap on mark were to drill wholes
Drill them out and slip the cap back on set the rivets
Put pipe back on and enjoy
Here is what the inside will look like once cut in half!
I know that if somone would have shown me that I would have done it alot sooner! It shows How simple it is!