I have a 2007 A4 Avant with 2.0T and 6-speed. Under heavy load (like accelerating up a hill in 6th gear), the turbo is obviously operating perfectly up to about 2400rpm, at which time it suddenly cuts out, with an obvious sag in power. I can continue accelerating slowly until about 2800rpm, at which time it comes back in with a surge. I haven't observed this under light load or in a lower gear. Does anybody have any ideas about what might be going on here?

 

Wonder if that's the cam follower. When one fails it can cause a loss of power in high gear when accelerating or giving the car gas.