This is such a genneral question its rediuculous. the power you gain from an exhaust alone is so small its irelavent. That brings into account sound, which is so subjective there is no way to direct you or suggest an exhaust with out knowing your preferences. The next thing is there are exhaust from 150 bucks to 600 bucks we need to know what price range your looking at. Future plans should also be taken into account, because if your going turbo then a 2.5in exhaust would be your best bet, or NO after market exhaust untill you are turboed so you can run a 3in.