Get a mechanic's stethoscope and start carefully poking around with it and see if you can find what's squeeling. My AC clutch went out a couple weeks ago. After gassing up, I noticed there was no AC. Looked at the volt meter and it was WAY down when the AC button was in. The coil was totally shot, to the point of embedding bits of copper wire into the pulley. I have a couple extra 16 and 20v pumps and pulleys, so I put my spare 20v pulley and coil on. Of course, the pulley was a bit bent because that's how the motors wind up in the breakers in the first place, or the breakers are a bit rough with them, so I beat it back into about round. The belt squeeks a little bit, but I tracked it down to not a bearing, so I'm not going to worry about it.
Anyway, I'd pull the covers off and start it up and poke around with the stethoscope. You could touch the middle of a spinning bolt like on the crank, for example, or the bolt holding the tensioner bearing. Also look for any wear signs on the timing belt and the covers. Maybe the belt is rubbing against the cover somewhere. My 5SFE did that once on the original belt when it got a bit loose.