Sorry i cant help you then bud,

Usually though with overboost it should cut power when you hit a certain amount of psi every time,not irregularly(Sp)

And cant a standard ERST chip handle about 10-12psi anyway?I had one that ran 13psi on standard chip?

Think id take it for a rolling road fault diagnosis pal.Not all that expensive-Got to be better than getting belted by a car on a roundabout