It could be AM covering their asses also it may be more dramatic in a gt. The most noticeable negative thing is the quirkiness of the automatic when driving slow. that combined with a much more sensitive throttle response makes it uncomfortable for slow driving.
"Race (91 - 93 octane) - The race tune will ensure the largest increase in vehicle performance. Using the highest grade of fuel available in your area is mandatory. This file is designed for "Race only Use" as the timing, fuel, and throttle response settings are very aggressive. in fact, the adjustments are so aggressive, that we do not recommend it for daily driving as it may cause your vehicle to try to jump out from a stop and easily spin the tires. Finally, with the automatics, we implement entirely new shift points and firmness settings to further enhance the all-out performance of the vehicle." -AM