Why is my car making this noise?

1997 Subaru Legacy L 2.2l awd. 2 days ago I started hearing a squeal while driving. Inspected the belts and they look fine, tension is fine. Now, the squeal is continuing while idling, the car is very sluggish during acceleration, I am guessing its like its misfiring. The motor shakes quite a bit at lower rpms with a medium ranged knocking sound. From the research I have done, my best guess is the harmonic balancer. Would that be a logical guess?