Some sort of short ram or cold air intake for sure, stock is just to restricted. With more air coming in, almost have to do exhaust to really feel the benefit. Get a machine shop to bore out your throttle body some, and put in a new plate. Also anything that is rotational mass, like rims, pullys, get lighter versions, you would be surprised how much more oomph your car can have with some lightweight forged rims. Probably easiest way to get the most bang for your buck would be some sort of nitrous, best bet would be a wet kit. Throttle body spacers dont do crap for performance, but if you plan on going the nitrous route, a throttle body spacer is a good place to drill and put your nozzle.