Are there any usual suspects for which pulleys go bad on the 4.0L w/ Bosch?

I have an annoying squeal coming from the accessory drive. I took the belt off and one of the pulleys is noticeably distorted-- it's plastic and has an almost out-of-round look to it. The bearing doesn't seem shot however, it spins nice and true like it should. This is the smooth pulley that sits next to the belt tensioner, I believe others have referred to it as a guide(?) pulley..?

The other pulleys (tensioner pulley, and idler pulley on other side near A/C compressor) look okay, as do all the accessories like alternator, water pump and such.

One oddity worth mentioning is that before I changed the serpentine belt, the old one kinda weeble-wobbled back and forth as if something weren't aligned right. Once I put the new belt on, I stopped noticing it, but the squeal still remains at certain RPMs.

Which pulley should I try replacing first? My thought is the distorted one, then go from there. Where is the best / cheapest place to get the pulleys? I don't mind getting no-name Autozone stuff either if they carry replacements.

 

Also, Rockauto carries two pulley sizes: 100mm and 90mm. Does anyone know which is which? Suppose I could take the belt off and go measuring pulleys, but would like to avoid that extra step.

I have a bunch of other stuff to order of Rockauto so thought maybe I could add a pulley and combine shipping, but don't know which pulley is for what...

 

There's 3 pulleys:

Tensioner puller
70mm idler pulley PQR500060 ($20 from Rovahfarm) (located just under the tensioner)
80mm idler pulley PQR101150K (located by the AC compressor) (you can replace the bearing (6304-2RS))

 

There are 2 idler pullys. The one by the tensioner is the 70mm. The one opposite that one is 80mm(I believe). The tensioner is the 100mm. Do yourself a favor and replace all three if you can. I didn't and now I'm finding that as soon as I replace one whine under my hood another one surfaces. Don't just get the pully (100mm) for the tensioner. Get the whole thing. I believe the 2 pullys beneath the coolant bleeder are more common to fail. It's not worth leaving it to chance

 

Change the pulleys out, the bearings WILL fail at sometime. I keep the old pulleys in the rig with an old serpentine belt, just in case someone looses a bearing and it drops the belt, you will have an extra.