Thanks everyone for your feedback and advice.

HoyaTerp - The whistling happens anytime you lightly press on the gas pedal. However, it is more pronounced when driving.
As asawadude suggested, I'll have some friends take a listen to try and pin point the location.

It's a high-pitched whistle like that of a cracked window.
Seems only noticeable at low rpm's, regular engine sounds probably cancel it out at higher rpm. Not sure if it could be coming from the torque converter. No connection between speed and shift lever position.


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heres the thing it is normal when you hear a sertain whistle that is comming from the air box where the engin is sucking in air at a certain speed you can hear this but the whistling that i have is not this and the dealer doesnt understand that i can the 2 different wishtling sounds i can distinguish between them. i know the air sound is normal but the second one cant be not for me atleast its jsut no i havent heard in any other x5 that i have drove so it isnt normal!

thats the problem for me it only wishtles are about 50ish mph odd huh and u have to hav your foot on the gass appling it very slightly and its so lound i can hear it over my stereo when i have it up about half or so i know thats hard to think wuts half but if i can hear it over music its lound for me and unacceptable

i might have to get a microphone and a couple actually and set them up in the car and do a test drive i think thats going ot be the best option. Last time used a video camera and mounted it under the car right near the driver suspention to prove that there was vibration commiing from the axle and ti wasnt alligned the video showed that the axle was vibrating up and dwon like more than 2inches and it wasnt always the same motion either so camera never lies......

That sucks i wonder if the 06s have the same whistling problems

If you remove the air filter cover and air filter and step on the gas as you would to cause the sound, does anything change? And if you repeat the process with and without A/C or heat running? Any chance it could be related to the A/C compressor?

For me, the car has to be in motion for the second whistle to be activated basically. Heres the thing tho....my dad had a gmc 2500 vandura van..and we started to hear this whisteling sound and after like 2 years of neglect guess what turned out to be the problem...the .... rear diff and after it was replaced with a used one but still a new one the sound disapeared that is why i am worriend a bit about the sound....its so similar however dealer claims is normal its just hard to pin point where its comming from and if its being caused from somekind of failing part of what....

I'm going out to try removing the cover and filter. I'll let you know if it makes a difference.

No change after removing filter cover and air filter.
W/ & WO Air compressor on.

Thanks for the idea; let us know if you think of anything else.:thumbup: