doesn't affect the car in any other way other than when your coming on boost and while boosting it can just judder/hold back/ intermittently sometimes it will pull through it sometimes it will get worse and feel more like a misfire.its had a new map sensor plugs coilpack air flow sensor boos hoses and it has no fault codes stored in pcm and on live data doesn't show enough data to highlight an area where I can go to so I'm thinking its got to be a mechanical fault like actuator / turbo.i had a st in yesterday and it drove so cleanly throughout rev range on boost so something not right!!!!