dac2800

I got a new (to me) 2016 A6 3.0 yesterday, and have noticed that under hard acceleration I hear a noise that sounds like it is coming from the left vent/dash. The best way I can describe it is like paper fluttering in the wind. I only hear it under hard acceleration, though it is a little more pronounced at higher speeds. I plan to take it in, but any thoughts would be appreciated. (I note that I had a mechanic go over it before purchasing and it checked out fine.)