ok so i'm in the process of tunning up my hatchback w/b18. obviously i'm going to have to go with custom exhaust. it's got one on there right now, but i think its too big. whats the proper size piping for this engine with dc sport headers, and j's intake. i'm sure theres some internal mods as well as minor bolt ons. i think it has a zex FPR, so i know there was nitrous on the setup. but i really need a n/a piping size. thanx in advance