Hi
I read about your post "Audi A6 2015 - Problem with brand new car", about some problem damp/low knocking noise. I have almost the same problem with my car A6 2012 2.0 TDI (in the same condition that you post), and I visited my Audi service and they checked everything and they didn't find any problems. I write to you because I want to know did you find some solution for your/our problem. I am writing you from Bosnia and Herzegovina. Respectfully Slaven