I have the same problem with my Lusso (w/automatic). When shopping for my 124 I test drove a Lusso(w/automatic) and that car had a high pitched whine much like the sound when alternator bearings gone bad. I told the salesman that didn't sound right and he told me that was just the sound turbo's make. I didn't believe him and the turbo is on the other side of the car. I also test drove a Classica(manual) and that car did not make the whine at all. Since I wanted the leather seats and premium collection I purchased a Lusso(only available w/automatic). The car I purchased was from a different dealer in another state and I noticed the whine a day later. Here are some details I have observed:
1) This whine is high pitched and sounds to be coming from the right side of the car.
2) It is far louder when the car is cold but never completely goes away(the noise level can over take the radio at normal to low volume)
3) When you corner with the engine cold, such as turning in an intersection at 15 mph, it sounds as if it is sucking up air and fluid or as if an engine bearing is spinning.
4) The whine seems in sync with the RPMs. Higher RPMs = higher whine. If I am coasting around 25 MPH with the transmission in neutral and fluctuate the throttle the whine will fluctuate as well. This mostly goes away once the engine warms up.
5) If driving by a wall on the right side of the car with the right window down, the whine is incredibly loud and almost to the point that is sounds kind of cool and like a jet engine. That diminishes quite a bit once the engine is up to temperature.
7) Common sounds and volume I would compare it to are bad alternator bearings (caused by over tensioning the belt), power steering pump that ran out of fluid, bad races in a differential bearing.
I've owned the car 7 months and I have 2,600 miles on it. I should take it to the dealer, but my local dealer has a questionable reputation and I hate to have them mess with my car.
Are these the same sounds you are hearing? Did you ever take your car to the dealer?