The noise you hear is an acoustic cavity resonance. The frequency of the sound is controlled by the interior volume and the excitation is controlled by the size of the window opening and in part by the angle of the window to the on-coming air. It is built into the design of the vehicle and there is nothing the dealer can do about it other than disable the rear windows or put a plexiglass wall between the front and rear seats (change the volume). By opening the windows or sunroof you have effectively changed the volume and can reduce the interior boom. But, if you want to run around with the rear window open and everything else shut, you better crank up the subwoofer.

97 Red 850R 45K Stock for 5k more miles