Hey mate,
Was it tuned on a 2wd dyno? Might have clutch pack problem if you did...
Can you jack it up so all 4 wheels are off the ground? If you can, spin the rear wheels. If the front wheels turn as you do, you still have pressure in the ATTESA system. If not, you might be in strife. Best case, the clutches took a beating but are ok and you just need to get some more fluid in the system, check the reservoir in the drivers side rear.
I have the R33, R34 GTR service manual if you can get access to a consult box; it will tell you whats going on...
good luck, pm me if you need anything.
m