The proper diagnosis is done with a secondary waveform from a Scope ..
But, most DIY do not have that equipment.
So, we tell them to change the coil to plug connectors under each coil as they are notorious for misfire and should be done as general maint.
Most Techs just change them when they do plugs b/c of their known misfire cuases.
Also, these systems don't like Plats at all, so consider the correct plugs.
If your plug connectors are old, I would just do them..at $4.00+ for gas,
you certainly need a well running engine..............

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A Dalton