My friend, I found the problem nevertheless, all the x5 have the same problem which is a crack on the air intake elbow which is the one that connects to the engine. The Rubber Elbow part cost $15.00 dollars at the dealer and will take you about 30 minutes to replaced if is your first time, all you need is a small socket and a screw driver handle to reach the clamps which are only two. I hope this will solve your problem as it did mine. In addition, when I first noticed the noice I took the car to the dealer and they told me that it was normal to have that noise, however, I do not have that noise anymore.

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X5 The Lost Mechanic