Initial thoughts -
Is the occasional stall after a hot restart? If so, it is typical behavior, but a fresh set of plugs and a clean idle air control valve will usually reduce the symptom down to not noticable.

Have you checked thoroughly for vacuume leaks? They can be intermittant. If you have not replaced your intake manifold gasket, you are due for one. (easy to do)

If you have not replaced your crank position sensor, you are due for one, unless '93s had better leads than the earlier years.

My '91 has knocked under moderate load since it was new. I have always had to use 89 octane to avoid knocking.

Power steering - The steering in my '91 has always been heavier than the steering in my '90, which in turn has always been heavier than the steering in our '87, which is feather light. The S70 is the heaviest of all. Is this heavy steering a new development?

Try replacing your power steering fluid before spending a lot of $$. That fluid is pretty old by now.

My '90 used to be heavy and groan when cold, then clear up when it got warm. It also had a nasty clunk inside, and shot inner tie rod joints, so I put in a rebuilt rack and fresh fluid. Smooth and light now.