If would first determine whether it is in fact misfiring, by removing leads in turn and see if there is any difference in the running of the engine, if not those cylinder(s) are the problem ones(s)

If so, maybe try swapping the plug/lead with a good cylinder(s) and see if the problem moves, if so then the lead/plug is the problem.

Certainly does not sound electrical related to me more ignition, possibly even fuel related.

Also do you have all four 'lugs' intact on the crank pulley?

Martin