To have or not to have....that is the question
 

I currently have a 1 5/8" unequl headers, 2 1/2" h-pipe with hi-flow cats, and 3 chamber mufflers with 2 1/2" chrome tips all from MAC. The quesiton is how much of a HP gain is the off-road H-pipe then the H-pipe with the Hi-flow cats? How much louder will it make my car? Will I still pass emission tests?

My friend had (before he moved) the same exhaust system as me except for he had the off-road H-pipe. His car sounded quieter for some reason :confused: He also had emissions hook ups and he could get away with it. If need be, I will swap the H-pipe when the time comes to get it inspected and then swap it back to the off road. I like loud cars and my car is LOUD but I live in a quiet neighborhood so I have to keep it undercontrol.

I don't think there is that much difference with cats or with out. You might be losing a little HP with the cats,but not a noticeable one. The biggest difference is ths size of the pipe, which you already have.

i know when i swap from my mac off road H pipe to my one with cats for emissions i can notice a difference. the exhaust is not as throaty and kinda dull. there is also a slight heisitation in acceleration. if you were thinking of a mac H pipe i would get a pro chamber, i have heard good things about them.