4Runner squealing when idling + in gear

Good morning!
First post on the forum!
I have a 2001 4Runner SR5, 243,xxx miles that I love to death - she is still my daily.
I have done all the standard maintenance plus had the timing belt, radiator and transmission replaced.
The only thing that is currently bugging me at the moment is as the title states, the truck squeals when idling and in gear (forward or reverse) at low RMP.
I have looked at belts and they don't seem loose and have also thought it might be the torque converter.
Any thoughts?

 

Bad idler pulley?

 

I will check this out!

 

Use a spray bottle with water to spray each pulley. When it quiets down for a little bit or changes tone, you have found the offender.

Can also use this method to see if it's the new belt that is squealing.