ok so ive searched around for and answer to this sound and it seems that a turbo on its way out makes this drill like noise. but everyone who has had this problem gets it when thy step on the gas and it spools up. now my a6 2.7t only has 60k on it and it doesnt make this sound when i drive only right when i start the car for the first time of the day and it only last maybe 2 or 3 seconds. now this is a noob question but when u start ur car do the twins spool up? even if so could this be the turbos or sumthing else. i was thinking maybe the oil pump or sumthing?

 

never mind its the secondary air pump