Had a Steeda Tune for my Mustang GT. It was a vast improvement over stock but I wouldnt say it was to the level of some of the other tuners (Especially those who review logs, work with you through revisions, and dial in your tune). My ST has had tunes from Unleashed, Livernois, and now ZFG. All were noticeable improvements over stock but I have stayed with the ZFG tune as my ST seems to respond the best to it. Its a 93 tune but I usually run ~E20