At speady speed around 90 MPH a whistling sound is heard. It is not aerodaymic, it is not related to engine RPMs or gear in the gearbox. As soon as pressure in the accelerator pedal is increased or decreased, sound stops. MB dealer could not identify what it is. Changed differential after instructions from AMG. Sound remained the same. Another 2 A45S cars were tried however and they made the exact same noise. To me it is not normal. Anyone experienced the same noise in your cars?