Strange sound on 3.0
 

Noticed lately that when I accelerate gently, around 2000 rpms I hear a sound like low pitched wind moaning. Doesn't seem to happen at higher speeds, just when setting off unless higher speeds mask the sound. Ideas?

I had a similar scenario on my E46 325i - low whistling or rushing sound at low rpm / part throttle. It turned out to be a cracked intake boot between the air flow sensor and throttle body.