Probably not as much as gutting the precats... Instead of gutting the MAIN cats, you can get Race pipes (w/out cats) or get random tech test pipes that have a performance cat and you see a lot of gains there as well. Personally, I wouldn't gut the main cats, waste of time in my opinion. The pre-cats however are only there for the first initial start-up to burn away some of the more harmful chem. after that, that's what the main cats are for.
