[Biturbos4] Startup Noise 2002 S4

[Long, Scott G A1C USAF AFMC 88 SFS/S4W]

When I start my car after it's been sitting for a while (morning or
after work) it makes a high pitched whirring/grinding sound from the
left side of the engine for about a minute, after that it stops. It runs
and drives fine. If I rev the motor while it's making this sound, the
tone does not change at all, it stays constant. Because it stays
constant I don't think it's turbo related. 

Any ideas what this may be?


Scott G. Long