Mystery(misery?) vibration, I am determined to find a solution.

[Dragonslayer182]

I have a little bit of vibration in my sedan, do you have a problem with squealing coming from the engine? It mostly happens during squealing, and so far neither a belt replacement nor an alternator replacement (It was going bad) has remedied to problem, although they did both stop the squeal for a few weeks at the most. I also notice symptoms of voltage drop when it squeals. (Slightly slower windshield wipers, slightly dimmer headlights)