I was wondering if anyone who is experincing a whine in their engine ever resolved the problem. My 1991 M5 is still having this problem. I did notice something unusual. At start, after warming up, I would hear the whine at netruel(stepping on the accel), first and second gear. About 5 minutes later the whine goes away. Another 5 minutes passes and the whine starts again. So my guess would be something that is thermostat controlled. Would the airpump be the issue?