Well if you look at 112 mph the dyno graph is showing about 400 hp and 360 tq if I'm reading it right.
400 hp x 5252 / 360 tq = 5836 rpms and a couple of mph above that it drops off. So 6000 rpms does seem to be the end of the road.
I now get why 5252 don't happen at 88 mph, cause the torque and hp are scaled different so even though they cross at 88 mph there not the same hp/tq amounts there.