I took all the stock air-intake hardware out of the car, put a large K&N RIGHT on the throttle-body, and put the air-temp sensor out of the way of any heat at all, to fool the computer into making it think that the air its breathing is colder than it is, therfore giving it more fuel per stroke, compensated by the extra air from the filter directly on the throttle body.
this made a noticeable power difference, and completley changed the way the car sounds.
this route is also extremley cheap.... all you buy is the filter!!
my wife even made comments when she took it for a drive, before i had told her what i had done.