The problem is intermittant b/c of the type connection to the plugs from the connectors. Those 3 do not Snap onto the plug like the open ones do..they
are a compression spring and it is the coils placement that holds them down.
If you take one out, the thing to look for is the connection inside the connector that goes on top of the plug..if you see these are grayish colored , they have been arching and it is time to replace them..they take a beating b/c of this poor design in the connection and they are trapped in engine heat b/c of the coil on top , where the others are open to some breathing and heat dissipation..which is why they do not have the fail rate as the coil ones ..so , that's about it...a maint. item, just like the plugs.
One wants to remember that a coil fires TWO plugs on this type Waste Spark DIS system, so if the coil connector fails, the next plug is in series with that one so the misfire is amplified...along with the fact that the ECU is programmed to cut fuel to the injectors everytime it sees a misfire..so, no gas..compounding the skip....
See why we change them????
I would also check and see if you have the old part# OVP...that is ECU feed and a common intermittant problem..if it is the old #, chage it regardless or you will just get stuck when you don't want to be.

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A Dalton