i had a xcal 2 for my v6 made a hell of a differance i had it programed for hrder shifts and for the 4:10s i was planing on installing. just be careful who you get to do the programing because the guy i used screwed me i ended up having to put a new motor in

you can buy your xcal from a reputable shop (Steeda Ford Performance Parts - Steeda.ca, www.mustangpowerparts.com,etc...) and have it tuned for your car with your mod.

Or purchase with a CAI and a set of mail order tunes.