1986 Other Subaru Models Subaru hesitiates, loses power

All of a sudden, literally from one day to the next, my Suby started missing and losing power big-time. A mechanic told me it was the cat, so I had that replaced and it still ran really bad when it got up to temp. Took it back and the guy replaced the plugs and the ignition coil.

BUT, it's still missing a little and the tach is flipping all over the place ( not as bad as it was).
Could that bad ignition coil have caused other electrical damage?

I hate that hesitation it still has. It usally runs like a top. One of the best cars I've ever had.