Try
http://www.rpmoutlet.com they have some great things for your mustang. But if you want some get up and go, power might not be the best first thoughts. Try gears, you'll move through your gears quicker and feel like you're tons faster and actually will be on take-off. But if it's performance your heart is set on then start small like exhaust(X-Pipe and duals)I went catless but it's illegal. Throttle body spacer and intake spacer would be ok. A nice flash tuner lice an X-Calibrator(look that up)or Diablo Predator. Under drive pulleys and cold air intake is alright. Man just start looking stuff up and look at other forums theres tons of info out there! I hope I helped.
Brandon™