Power steering pump (as most of other parts) are actually mounted TO
the engine, so engine mounts (connecting the engine to the chassis)
has nothing to do with it. You might want to check the (vertical)
alignment of the pulleys, I have seen a similar problem when the
tensioner was incorrectly positioned (with a washer under it) and
therefore it was out of line with the other runners causing the same
problem with the belt.

OK, the main crank pulley (harmonic balancer) is a two piece part that can
separate with age. The pulley drives the alternator and the water pump outer
pulley. The water pump inner pulley drives the steering pump.

If we assume that there are no extraneous washers present around the water
pump pulley set, all the belts should line up just fine.

Lets suppose that the water pump bearing has a problem: this could result in
belt misalignment. The question now becomes "what is causing the water pump
pulley problem?".

This is what I suspect:

worst case:
Your engine is the 7 bolt 4G63 type that often suffers from crankwalk:  this
is the failure of the crank thrust bearings allowing the crank to move
forward and back. (This is NOT a good thing, and fixing it requires a
COMPLETE engine rebuild, or replacement with a 6 bolt engine). When the
harmonic balancer was replaced, the mechanic may have noticed that the
alterator belt did not line up properly (because of crankwalk) and put some
washers under the pulley. Its not easy to put them between the two pulleys.
Here's instant belt misalignment

best case:
you have some wrong parts on the engine: eg the wrong water pump that still
fits but misaligns the belts. PS pump from an earlier Eclipse.

I think you need to get the car to another garage that specializes in
Mitsubishi turbos. Get the pulleys off and have the engine checked for crank
walk. Other symptoms are difficulty changing gears and the crank angle
sensor failing (actuallty being destroyed) .