There is performance and performance of course
A decent cat-back exhaust has to be first IMO, much better thottle response and it sounds nice too
Mine cost me under $300 and was the best $$ I spent in the car.
Cold air induction is money well spent too, tho' I haven't been that route (yet) for much the same reason and not too exxy.
Nice short throw shift puts a smile on your face even if the car doesn't go any faster.
Performance also equals handling.
Thicker rear bar, lower/firmer springs and camber kits each end will give you more corner speed = performance