Thanks for the advice, Bill.

The problem seems to happen even with strong local stations. The dealer already checked the antenna connections which are OK...and I haven't had any problems regarding reception of stations. They also pulled the control unit for bench testing...which was OK. I just notice that the stereo effect comes and goes while I'm driving (yet the 'stereo' indicator always stays on...which is odd). I think it's a calibration problem within the tuner. I tried the same stations on the same roads with my Toyota, and they play fine. I asked the dealer to temporarily swap it with another one...just to see if it works differently, but he says he needs additional approval for that...which was three weeks ago.