Be aware, a friend of mine put a gibson exhaust on his 00 2500HD and it kept burning up the rear O2 sensor. He went through 3 before putting the factory exh back on the truck, and never had another problem with it. This is the only time I've ever heard of something like this but it is something you may want to consider. Another friend of mine has a 04 2500HD and at 6k miles had a custom exh done at Lou's (Plymouth) with a singe inlet/dual outlet Flowmaster 3 chamber. He's got almost 40k miles on the truck now without a single issue. Just some food for thought...