AGV, my suggestion would be to look very closely at the connection at the coil of the troublesome cylinder. If there is a poor connection there between the blades of the coil and the wiring harness connectors, that can cause misfires (speaking from painful experience here, and yes, I always now think all misfire problems are like mine, but one of these times I've got to be right! ). If you see any signs of pitting or blackening on the coil blades, this may be your problem. If so, try cleaning the blades and inside the female connector with a sliver of emory board or something, and then make sure when you re-connect the coil that it is a snug fit. I ended up just replacing the female connectors and was shocked at how much tighter the coil fit, rather like trading in the wife for .....oops, mind wandered to the gutter there for a moment, sorry. Anyway, I hope that helps (or at least gave a nice image).
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-Jim
'93 MC21