Lets get this straight it is not a nistune issue as much as an incompatibility between some Z32 ecu's and the R33 car itself, we have done about 20 or so (upto 400rwkw) and of those 20 about 6 give major headaches (r32 nistuned ecu worked so its not the cars), since i cannot differentiate the exact problems between ecu serials and r33 model series1, 2 or 2.5 i have stopped doing them, Stao's latest issues were the 16bit ecu.
Nistune is a great system and is generally our Number 1 recommendation for S13, S15 and R32 / R34's.... just not R33 with ecu conversions