i have a 2006 gt auto with magnaflow exhaust (too quiet) and kn intake today i got the x2 hand held tuner---- i have it on the 87 octane program and wow what a difference on throttle response and shifts i cant imagine it with 93 octane one question though the sales guy kind of scared the hell out of me he said if the ford service guys reprogram my computer (without me knowing) and i go to put a tune in my car will die !!!!!!!!!! the sales guy just said to be sure and tell the service guy about the tune and not to add any new tune when he works on it. has this guy ever been to a dealer for service - just cause you tell the first guy something does not mean everyone gets the message any suggestions. thanx stangnet rules-- best mustang site on the net !