i have a question, i like my cars loud, ive always cut the cats off and straight piped it all the way through. where the cat is i put a 1 1/2 restictor tube welded inside, im wondering if anyone else knows the exact peice to put in to keep the proper compresion?

 

Compression? Are you referring to velocity or backpressure. Why would you want to put a restriction in your exhaust?

 

need some more info on your car to determine the size of the cat