Any idea's what could be causing it? Boost seems to come on then off then on etc when the car is hot. Started doing it on a recent track day, but once left to cool down was fine on the way home. That was 3 or 4 weeks ago and all had been ok until yesterday on a motorway run the same thing started happening in 4th and 5th gear. Car is a MY00 with ppp and decat. Have I knackered the turbo or is it likely to be a sensor of some sort?
Any help much appreciated, James

 

Probably overboosting. Search on "overboost restrictor PPP"

 

Tks John, I'll have a look