...LAST! If You believe there is any possibility that One or More Plug Wires may be Arcing to Ground, or Crossing-Over Together??
Try the 'Total Blacked-Out Test'. Where the Deck is opened for an Observer (you), In a Garage, All Lights Off, Blacked Out, and a Helper starts the Engine (always in Neutral) and gives it a Couple of Moderate Revs.
You might just be Amazed at what You Observe!! And check the 'Coil Wire' and D. Cap, Also. All 'Things' will be Revealed!
"Try It! You'll Like It!!"
MJ