R32 Gtr Loses Throttle Randomly

[Chris32R]

My R32 GTR whilst driving randomly loses all power and the revs start dropping down even when the accelerator is pushed down. It has stalled on me a couple of times when I have put my clutch in and sometimes the idle gets pretty low and struggles to maintain a constant rev. It usually happens after a bit of driving (over 10 minutes) and will sometimes cut in and out. I pulled over once when it lost power for a good 30-60seconds and turned the car off and then on again and the car went back to normal.

The car is going for a re tune with PFC D Jetro in a couple of weeks time. It currently has a nistune with rebuilt forged bottom end and N1 turbos.

Any ideas on what the problem could be and if it is bad for my engine for it to be doing this? (don't want to blow or damage an expensive motor).

Thanks