I posted this in the new member forum, but decided to repeat it here. Has anyone else experienced this oddity? My 2003 SL500 has a peculiar buzzy vibration when either accelerating or decelerating through 2100 RPM. This occurs only when the car is driven, never when revved in neutral. The noise seems to be coming from the rear end of the car, but that may simply be the way it's channeled to the interior. The dealer, who has always been helpful (inexpensively cured my rattling top issue) wants to hold the car for monitoring purposes, but it's difficult for me to give up the car for any length of time as it is my daily driver. Another, independent mechanic, identified a broken tail pipe bracket, welded same, but that didn't stop the buzzing. It only strikes at 2100 RPM!