Ok well my friend was wondering, what size throttle body to put on. He also has a 2003 mustang gt, so this information actually might benifit both. Anyways, the only mod he has done so far is a CAI with catback exhaust. He wants to do a plenum upgrade too but was wondering what size throttle body to do. He is looking to get headers, and mid pipe this summer. Also, he might be doing a kenne bell supercharger next year. So what do you guys say?