My problem was that I had very low compression on cylinders 2 and 3. I had my mechanic work on it and my car seems to be running better... for now.

I bet your friend's component was probably the main relay -- this, I've already checked a few times and even did the DIY rework so I know it's working fine. Another article I read mentioned the distributor coil as a common fault in the '91 -- I've also had that replaced recently as well.