I say, a hi-performance muff (search the forum for the different opinions), hi-performance brake pads and sticking with stock sized street tires are your best bet for spending some money... not a lot (check Tire Rack for reviews on tires). On the street, big tires and wheels decrease off the line performance, hp at the wheels and braking performance.
I also cleaned my stock throttle body, when I had it, with Seafoam (search the forum again). I added a K&N intake with an AEM Dry Flow filter for better throttle response (very little hp gain) but there's a cable mod that will help too.
Just about all my mods came from searching the site. This site has a pretty awesome brain trust of knowledge on Ex's.