SHELBY GT 350 Member
Joined: Jan 2011
Location: Central Massachusetts
SCT seems to be the de-facto standard for the S197 (2005-2014) Mustangs and I assume it is the same for the 2015+ S550 cars. The basic tuners can do basic stuff like download a custom tune (that someone else wrote for you) and I think you need some of the higher end models if you want to do more technical stuff yourself, like a dyno tune where you might want to advance the timing.
As the factory tune becomes better and better, there is less and less left for aftermarket tuning to tap into . . . but I think there is still a little left.
Hopefully someone else with more direct S550 experience will chime in
| 2010 GT coupe | Daily Driver with some Steeda and GT500 take-off stuff for the occasional track day