More than likely you are having a boost deviation fault You are either getting over or under boost. This is normally caused when the turbo waistgate vanes get plugged or restricted with carbon build up. The only way to properly diag this concern is to be able to scan the vehicle and test boost presure. When the engine control unit see's a boost deviation it will go into limp mode, but once you restart it resets itself.
David DeLeon, VW Master Technician
More than likely you are going to have to replace or have the turbo rebuilt. You are getting a boost deviation caused by the waist gate unable to regulate boost. Sorry but that is all that you can do. This is assuming that you checked all the charge air lines and have no leaks anywere.
Sounds good. Please let us know if you need further.