2001 4Runner: Screeching sound - Need help

Hey everyone,

Long time visitor, and second time user. I have a 3rd generation truck that started making this noise during our first cold snap in Columbus about 1 month ago. Here is a Youtube video link to the engine and sound.... It is titled:

3rd gen 4Runner - cold weather screech

https://www.youtube.com/watch?v=WimarkAjvak

Here is what I can tell you:

1. All 3 belts are fairly new
2. The A/C idler pulley was replaced 9 months ago.
3. The alternator is brand new
4. The power steering pump is not the culprit - verified by Toyota mechanic.
5. It only does this on very cold days (we have had a lot of them), and ususally after truck has been sitting and engine is cold.
6. The timing belt, water pump, tensioners, etc. were replaced 30K miles ago.

I think it may be the a/c idler pulley again? (I used the Gates 38031, so it should be OEM quality)
I am thinking it could be the fan cooling bracket?

I have a stethoscope, but cannot totally pinpoint the noise. Any help/suggestions would be greatly appreciated!