yeah what are you trying to do with the car? you just want a few extra hp and a good sound, then bolt ons are enough. if you want all-motor power you will have to get into the internals. if you want to go boost you can either keep it pretty stock and get a turbo or supercharger kit, or go all out and build it for boost, and make big power.
anything beyond your basic intake, header, and exhaust and you will want to get some sort of engine management and get the car tuned.
you gotta tell us what your goals with the car are.