Before i go and pull things apart i was wondering if anyone had any idea, 89 ERST chipped, oil seperator, K&N, stainless system,, full samco hoses,

i took the car on an air strip the other day and noticed a problem when boosting, it seems like it is loosing power and the rpm slows or stops, it always seems to do this when it reaches max boost which seems to be just over 1bar on the boost guage, at first i thort it was the clutch suddenly slipping but then the revs dont rise! ive been told it could be the chip not hacking it as the boost is to high,

Also it is idling at 500rpm just lately, any one got any idea?