I have the same issue in my vehicle, whistling noise sounds like its coming from the center console / AC vents at high speeds 100+ ... sucks ass.

 

It looks like windshield leak is a big suspect. GL Kevin. Hope you get it fixed for good.

 

I had a very similar noise on my '95 E34...turned out to be the driveshaft. I would think you do not have enough miles/age on the car for a driveshaft though...but mine sounded just like that and only happened at about >75 mph.

I also had a very similar noise on my E34 AND it happens on my '08 535i. On the E34 it was the driver's side top exterior windshield trim/seal was loose and flapping in the wind...kinda like a reed effect when the wind hit it and it made a "singing" type noise. My '08 535i does the same thing when I get over ~100 mph. Dealer said they "couldn't duplicate"...so I haven't addressed it yet.

You should be able to distinguish if the noise is from the windshield (high up in front) or the driveshaft (sound comes from under the center console).

 

I have heard that about 3 times on my car... maybe around 110mph. The first time it happened it scared me to death... I thought it was some sort of siren. If I speed up or slow down a little it goes away. It just lasts for 2 seconds or so.

 

thats definatly an air leak