Originally Posted by Pankakez & BMWs
I think Jeff may have it. But I have never experienced this till today actually. So I can't say I agree that the sound is normal. It does go away if I blip the throttle and reoccurs when the RPMs get back down to ~600.
Yes, that is normal. That is the fuel pressure release valve. The HPFP pushes a lot of pressure that is excessive at idle.