Q: Loss of power and squalling noise

A bad harmonic balancer typically causes a vibration or knocking noise, not a squeal or loss of power.

If the squealing noise is coming from the belt area, you likely have a problem with any of the other components of the belt system dragging on the belt. First, the belt tension needs to be inspected for deflection or being loose. Next, the noise needs to be limited down to an general area of the belt system. After that, remove the belt and each pulley (alternator, power steering, tensioner, A/C) needs to be tested for drag or lateral play. Even a dying battery can cause the alternator to overwork and cause a belt squeal. A basic inspection both visually and physically should indicate a problem. A dragging pulley can cause a loss of power.

If the squealing is not coming from the belt area, then it needs to be pin-pointed to where it is coming from.

The loss of power could also be related to a weak fuel pump, a clogged catalytic converter, a bad mass air flow sensor, a slow oxygen sensor, or a vast list of other less common items. If your check engine light is on, I would have the codes scanned and address those first.

Maybe the two problems are related or they could be two completely separate issues altogether.