E46 General
Below is a link for some audio I recorded of the noise:
http://www.youtube.com/watch?v=lPIjHTQ2xFQ&context=C2b40cADOEgsToPDskJMqxo6Lw9L1b6360mw9unK
It only happens on a cold start and the frequency increases with RPM. After hitting 2,000 RPM or warming up, it goes away.
After searching...