My '01 X5 4.4i sounds like it has asthma
 

I've done some searching through the threads and it seems like a few others have had this problem.

General description: Upon starting, I get a whistling/whining sound from under the hood - imagine a car with asthma - it's got that "old car sound". In the beginning, this annoyance would occur only sporadically and used to go away after the engine warmed up. Gradually though over the past 3 months the sound has become more prevalent - staying audible for entire drives (30 mins+).

A shop I get work done at believes it is the secondary air intake that needs replacing and with (a lot of) labor, parts, etc may be around $900 to do the job.

From the threads I've found on this website, it seems like it could be a crack in the Intake Control Valve hose?

Any other thoughts on what this could be, how serious the problem is and how $$ it should cost to fix?

Thanks!

Sound like you've got a vacuum leak somewhere. With the hood open and the engine running. Listen to hear if you can identify the location of the sound. Look for cracked hoses and loose fittings. Use gloves to move hoses to see if that changes the sound. You might be able to fix the problem for free or the cost of a hose or fitting. Good luck