I assume this Nismo is all stock w/the Yoko ADVAN sport tires and the crappy viscous LSD? The viscous probably heated up after the first couple "beatings" when you were testing and basically it acts like an open diff once it's hot.
My suggestion is install a 1.5 way clutch LSD and some RE11s or ADVAN AD08s. Also, to get rid of that nasty wheel hop look into installing SPL solid rear differential mounts and SPL rear traction links.
Here's a
post on how to upgrade the rear differential.