if by messing up you mean will it throw a code; no it won't. will it be louder? yea. but i don't know how much louder.
Well I took off the resonator off and it sounds way better. So the question I have is when the header back exhaust from injen comes out would I be able to take 1 of the cats off since I have the PVEZ model, and my state only requires 1 cat. Will removing 1 of the cats mess anything up, like throw a check engine light on or something???
^ You took off the resenator and it sounds better... is that with your stock muffler? I dont know if you can remove the second cat altogether on the PZEV models. The reason I say this is that there is 3 sensors on the PZEV models... one before the first cat, one inbetween the first and second cat, and one after the second cat. Now if you remove the second cat, where does the last sensor go? You cant just leave it hangng there, the car will throw off ses lights 24/7... and who knows how that will effect things. I know magnaflow sells high-flow cats with the sensor mounts on them, so thats one thing you can do, switch the stock to a high-flow type... but other then that, I think all of us with PZEV models are stuck with the two cats.