Hahahahaa......two inch straight pipe.......jk......it depends on what kinds of modifications you have done. Most commonly you will see three inch exhausts or larger on any style forced induction car, and even some all motor cars. For the most part though, on most all motor cars, you'll be better off with some sort of 2.5 inch exhaust, usually either a japanese exhaust like Fujitsobo or the Jap spec single pass version of the Mugen, or something along those lines, either that, or something from a company like Hytech or SMSP. It all depends on what you're looking to accomplish...

Later,
Aj