There is a thing that will reduce engine power (FLR) to prevent brake overheating. It could be, but is unlikely to be, the thing you're experiencing.
desertman123 re-pointed-out this page to me when I was doing some coding:
http://www.onelapx1.com/blog/how-to-...w-actually-fun
Do your logs show power cuts? If not, then it could simply be the eDiff working (not true torque vectoring) by braking the wheels...