A pop charger is a waste of money IMO. It's just hooking a cone filter up to your MAF and scrapping the OEM airbox. Honestly, Minor Threat, go with a Hotshot header, buy a used one from someone if money is an issue (when isn't money an issue?)advance your timing a little, and put a CAI in. I built my own CAI for like $60, and that's because I bought a $30+ K&N filter instead of a cheap $20 cone filter from Autozone. Skip the damn catback, it'll net you oh maybe 3 HP at best. If your car hasn't had a tune up in awhile do that as well. (plugs, wires, cap, rotor, O2 sensor possibly, timing check). Keeping you tires at the proper pressure helps too, and that doesn't cost anything. I've heard good things about replacing the shifter bushing and they're like $7. No HP gains, obviously, but shifting is much nicer. As far as a store bought CAI I don't think it matters all that much. Some guys will swear one is better than another, but I think they're all the same. The only thing that would make one better than another would be the coating, ceramic is what you'd want, and the bends. My homemade setup has only one bend in it and it's a very smooth and gradual bend. I've seen shitty sharp bends on store bought ones before.