OK I've now seen this on 3 x R34s (my GTt being one)
I noticed a very strange intermittent shift in power in my car some months back, some days it would be going a fair bit harder than other days. Idle quality started to decline, braking hard would stall the car sometimes (very on and off) and the car had developed a faint slight shudder/miss on idle.
Today I turned the key, started fine...then 5 seconds later started to struggle, accompanied by a puff of smoke from the ECU kick panel and the smell of burning...oh noes!
I've opened up the ECU and the primary power transistor for the ignition signal has cracked above a very blackened 4th pin (exactly the same as the other 2 ECU's I've managed to look at)
So there you go, I have no idea why it occurs, it's rare but always seems to affect the same power transistor and results in losing a cylinder.
Lucky I had a spare 4AK19 Hitachi chip laying around to fix it