hii im having an issue with my ba xr6 turbo, during low boost the car boosts fine, when boost is higher there is a loss in in power, and it stutters, like there isnt enough fuel going to the engine, boost cuts than back in real quick after boosting for a long period sometimes the engine idle gets real rough for a minute or two than goes back to normal, when its rough idle it seems like all the cylinders aren't firing up, I thought the problem may be todo with spark plug coil leads etcc.. but it only ever EVER does it after long period of high boost.. im thinking it might be valve springs?? any other suggestions??? cheers FORD LOVERS