Did you ever get to the bottom of this? I'm at 68k and I'm also getting squealing on cold start (but not on acceleration or AC). My mechanic replaced the pulleys, tensioner, and belts, and it's still squealing on cold start.

Now he thinks it might be a bearing going bad on the alternator or a pump. It goes back into the shop this week to find out.

No, the mechanics are still clueless. Seems like a mystery till now. let me know how your diagnosis goes.

Finally found the squealing. It was the starter, which needed to be replaced. It's been about a week and it's not squealing anymore.

Cool. how much did you end up paying for the starter motor?

I'd have to double check, but between $450-$500 before labor.

The issue with mine is not discovered yet. Going to 3rd mechanic this time. let's see.

I'm not sure how much to believe my mechanic that he did this, but considering he fixed it, maybe I should: He had me leave it overnight in his shop so that they could get a solid cold start, opened the hood and had three other mechanics with stethoscopes on likely culprits to figure out where the squeal was coming from.