I own a 2014 Q7 TDI and have been experiencing an annoying droning/humming noise between 35-45 MPH. Dealer tells me this is normal? You can hear and feel it as vibration under steady throttle, with a slight pause with lift off but it resumes when coasting until speed drops below 35. Anyone else experiencing this and/or any suggestions? I've read many reviews and have not seen this mentioned as an issue.