i am thinking about doin a 2.5 exhaust but wut do i have to do to keep it legal. keep the cat and a muffler right?? is it worth it to do 2.5 the whole way?? it should free up a lot of hidden power right?? i have jus a muffler on it right now. i dont want to do a swap so plz dont tell me to do that. my car is a 93 civic with a d16. thx