I've "heard" that it's because they didn't want to spring for higher performance tires so needed to limit it to the tires rating.
Now, this could be speculation, but it is a ford and they have been known to cut corners (cough, cough).
A 115 limit is pretty sad. Imagine the point-by's at the track!
The drive shafts have been known to fail around 130mph
Sometimes, I see cops with their backs turned writing tickets. When I drive by I can see them stick their heads up,and sniff the air,catching a whiff of exhaust and burning rubber,the crimson smell of speed,telling them a Race Red Mustang is somewhere nearby!
2012 Race Red GT, Kenwood Navigation system with Metra dash kit,GT500 steering wheel,Steering wheel buttons INCLUDING BT enabled,Takeoff leather seats with seat heaters.