Hello, got a 2003 X5 3.0i auto
Have noticed when under light acceleration, for example lightly press acceleration from standstill (1cm on gas pedal) it causes an extremely high pitch noise from somewhere under the car, seems to left side as is louder when left window is wound down.
(If you have ever heard one of those high pitch dog whistles, it sounds exactly like one of those whistles.)

It only appears when accelerating lightly, so if you put your foot down or are stationary or even revving when stationary you cannot hear the high pitch sound.

Anyone got any glue what it could be? Was wondering if it might be waterpump or belts / tensioner???