I've had this problem with my 94 for about 4-5 years now.
It had a high speed miss. Running at 65 in 6th, when punching the gas it would stumble badly. it didn't happen very often, and downshifting first solved it, so it wasn't very pressing to fix. I took it in about 6 years ago for this, and they first blamed me for lugging the engine. After I demonstrated it by taking the service mgr out and nearly putting him through the windshield, they then blamed it on bad plug wires. After replacing those without fixing the problem, they then blamed it on the Optispark. When they showed that to me, it did have some rust in it so they blamed it on the leaky waterpump, which it was. That seemed to have lessened it greatly.
Fast forward 4 years of having this intermittant problem:
It recently developed a hard start and a hunting idle. I thought this was either a bad fuel pump or a bad fuel regulator. Not having a pressure gauge, I had the mechanic check when it went in for it's normal oil change. The regulator wouldn't hold any pressure (a rapid drop to 0psi) once the ignition was turned off.
When they removed the regulator, raw fuel dripped out of the vacuum line. After replacement, the problem went away.
Conclusion: if they say it's an optispark, check the fuel regulator first.
regards, charlie cave creek, az