hey guys,
i found what the problem was, too high boost, through my intercooler
i went to trackday on friday @wakefield park , and i lowered the boost from 11psi to 6psi, and this solved the problem. I did 10 laps straight and had no issues with loss of power.
most of time now i do 5 laps, then 1 slow lap, then repeat.
i think r33 has dual stage boost, as it goes up 6psi, but after 4-5krpm it goes up to 10psi, but i didnt have any issues.
anyways thanks for help, and do try wakefield park on weekdays, it was open track all day not many cars at all.