When I start my car when it is slightly cold (i.e. today about 30 deg...car is garaged) my 98 has what sounds to be a high pitch whistle. When I start to throttle, the pitch gets higher until it goes away at still fairly low RPM (under 2k). Once I drive the car for about 20 minutes it goes away. I popped the hood at start up and it was hard to pinpoint, but sounded like the AC pulley area..possible bearing???vacuum leak?? Anyone have any ideas here?

Thanks!

Try spaying some silicone on the serpentine belt when you start it and see if the noise
goes away. I had the same problem and that instantly stopped my sqealing noise.

I have a noisey AC pulley bearing and spraying the belt does not help. I'm praying for an early spring lol so I can replace it

I've already replaced the serpentine belt. This doesn't sound like a squeal. It is higher pitched and sounds more like a whistle (like air moving).

I can't think of any vacuum near the A/C pulley area. Turn the defrost on to engage the A/C clutch and see if the noise goes away.