Originally posted by chongo:
Stock exhaust piping, Omptimized Y pipe and a Magnaflow high flow cat will produce a louder exhaust,
beacuse more air is going through the exhaust system.

Also it's possible that one of the welds didn't get sealed properly.



But I don't have stock exhaust piping except one small little piece, but I see what you are saying. So basically the hi-flow cat will make the car louder, but I still may have a leak?