2004 530d problems

If anybody had any experience regarding following, I would appreciate your opinion. I have a '04 530d wich has been bought 3 months ago. In 50% of cases when driven fast (sometimes already at 110mph and sometimes not even at 140mph) there is a certain anoying sound wich was interpreted by the authorised dealer as a "wind noise produced by channels on the roof". He also told me that it can't be fixed. I would like to point out that it doesn't seem to me like wind noise at all but rather like some electrical interferences coming from the dashboard or speakers. I would also like to emphasize that this sound has not the constant frequence but is constantly changing although the speed of the car stays the same. I just can't belive that the BMW produced a car that "whistles" depending on the current mood. The other problem, although I can't be sure about that cause I have very little experience with BMW automatic gearboxes, is that the car can not stay on the steeper uphill when it is in a "D" position. The same situation is when I try to stop the car on the downhill, put it into reverse and release the brake; disregarding the "R" position, the car goes straight downhill. A friends '93 Mercedes 320 coupe stays firmly in place when I'm manouvering it on a steep downhill or uphill. The same did my old Audi. Now, my question is weather this behaviour of my BMW steptronic is normal or not. Maybe it hasn't anything to do with the issue but I think I started receiving "service needed" message on the display just as I started noticing the issue with the automatic. Since the car is in my possesion for only 3 months now and I wasn't driving steep hills till now, I couldn't say there is something with the gearbox because other than that, the automatic performs flawlessly in my opinion. Thanks for help. Mario