Originally Posted by MyLS1Hauls

One 3.5" pipe is more than enough for 400hp. It is plenty for 500hp even. The cross sectional area on 3.5" pipe is essentially the same as your dual 2.5". The stock cat back is the last place to look for power gains on a 6.2 truck. I wouldn't touch the exhaust until you add long tube headers, and even then, I'd still run the stock cat back.

Originally Posted by Bullhead00

So you're saying the factory exhaust on 6.2 trucks is 3.5" tubing from the manifolds back? If so, yeah, I could see leaving it alone. If anything, like was said earlier, cut the resonators and weld in a muffler if you want the sound.