i had a R32 GTR 92 model and when it was doing what you described was the wiring harness that goes to the ignitor there was a break in the wire somewhere there as i fiddled around there with coil pack cover.
not saying that is the cause but just n idea that may or may not help. BUt could be alot of things...AFM's? Coils? Ignitor?..if you have a friend with GTR would be handy, swap parts at a time.
GL with it all