Pulley - they're pretty cheap these days.

CAI, man. If you can't afford the CAI, toss the airbox and stick on a cone.

I'm in the same boat. I haven't done many mods to my GTP yet either. Actually, unless you count the $2000 stereo...

I've got an open cone on mine, I like it. It's not a huge cost, and I noticed an increase in my fuel economy as well.