My bet would be bad bearing but which one? Before going in that far, yes I hear the difference with the cover a bit open but noise can be weird, pop the serpentine belt long enough to see if the noise goes away.

Painemann, when I did my rocker replacement, I inspected the tb pulleys, and I've noticed one of them having more wear and tear than the other one. In other words, one seemed like new, one was spinning way too much and also had a little noise and very tiny bit of grease out on the rings. I had replaced mine with new about 25k ago, oem. Since it was still ok-ish (no play at all) and didn't have another spare, I put it back, thinking to keep an eye out for it, but my thought is that they aren't good quality. I would bet is one of your tb pulley. Side note, the tensioner seemed like new. I don't see what other thing could make that noise... if you took the serpentine belt out, take out the servo pulley and serpentine tensioner, the tb cover, get a long extension/screwdriver, put one end on the bolt (center) of the pulley, your ear on the other end and you should hear the noise amplified for the bearing that causes the noise.

I am going to check this soon! I will be cranky if I have to pull the belt, have to get the darn tools again. Is it possible to replace an idler with out loosing time, maybe have a helper hold tension and the tensioner is loosened? Wishful thinking!

You don't need to lock anything super rigid, all you need to do is make sure that belt stays on the can and crank pulleys. You could do this with small wedges of wood or even rags stuffed between the casing and the belt to hold it against the cam and crank pulleys. I wouldn't worry about small movements as long as the belt never comes off. You can use the allen key trick to work the tensioner.