I just got a 2003 328i and am looking for some performance mods within my budget (limited budget). What is the scoop on performance chips - any specifically recommended? What about exhaust?

I got the car with 94,000 on the clock and VERY clean. Very nice car. I started out with Signature Motoring performance intake which boosted HP by 12 horses. That kit for $194 with shipping. So I've got about $400 to spend (that was the budget)! LOL!