Has any other 435 driver noticed a slight rattle around 1500-2000rpm under normal acceleration in the first couple of gears? It seems to come from the underside of the car in the region of the exhaust and is only noticeable with the windows down (since the sound isn't loud enough to be heard with the windows closed). It's not a loud rattle, but it's irritating.
I took the car to my local dealership, but they couldn't locate the source of the rattle. The technician took me for a test drive in their 435 demonstrator and it also displayed the same rattle. I expected better from BMW!