I have the same problem on my 4.4 and went to the dealer 3 times for and they say it is normal. How can an annoying whistling noise be f**king normal. I am so annoyed that i had to walk out of the dealership before i flipped out on somebody. Then a FSE looked at it and said it was normal to. So i said if BMW says thats normal than BMW is a bunch of idiots that dont give a crap about the quality of the product they but out anymore.

So i just gave up and deal with it.

But if anyone ever finds a fix let us know.