Do they have one (factory installed) or are we taking about “lack of power churning 31’s with wind resistance of a brick”here?
I'm not sure, but at some point you're going to go as fast as the gears will let you go, so you're going to hit a point where it just can't go any faster. Of course it may be very hard to get to that speed as the aerodynamics alone will fight you as hard as possible.