so i had a cel light and i found out it was my oxygen sensor. then i replaced it and the light didnt go off. turned out that i have a bad catalytic convertor as well. cool. so i did some searching on the site and found that most people go for the carsound (magnaflow) high-flow cat. well, if im just doing a direct replace of the stock cat with stock exhaust on a 98 sh, im wondering if i should get 2.5" piping. will this work? i want to get the mugen exhaust (that is what i want at the moment at least...it may change, but i still want 2.5" piping and im going n/a), which i believe to be 2.5", so wouldn't i need a 2.5" cat? will the carsound cat even hook up to the stock exhaust?