Rep Power: 0

I'm thinking about installing an exhaust with piping going all the way back to the cat. Correct me if I'm wrong but is everyone going with 2 1/4" piping to the cat? Also, say in a year or two, I get enough money to do a engine swap(K20) I would be able to keep the same exhaust and everything right? The way I look at it, it's pretty universal and it wouldn't make a difference.

Thx,
sorry for the noob question, bare with me plz.