Flowing tracks are the real fly in the ointment here. Maple Valley seems to be almost in its own category because of the speeds involved. At Road Atlanta Short, you'll hit 120-130 in B class, it seems, using flowing cars, and do fine. I've hit 150 at Maple Valley, and not even in extremely powerful cars (My 2000GT was built at that track, and runs 241 bhp, usually 149 mph at the end of the straight, IIRC). At Road Atlanta, in C class, my MR2 and 914/6 both beat the 2000GT, but they were useless against it at Maple Valley, giving up over a second per lap. Maybe it's something other than top speed (I'm pretty sure the 2000GT enjoys a Charger-esque aero advantage), but that seems to be part of it. Admittedly, there are grey areas, but I think this may be the contributing factor.