Thats is the variable vane mechanism (the moving fins inside a Garrett turbocharger) and with carbon build up it jams and may set a code in the memory. If your turbocharger is wastegated(KKK) then you may disregard this thread as its operates differently and if faulty you should check for a stuck open/close wastegate that will trigger a overboost/no boost code and one should check the vacuum hoses for splits and cracks leading to similar symptoms. Generally KKK turbochargers are a bit more reliable but the Garret ones are more common and easyer to tune and much cheaper...!