[Capt. Debbie]

I think you nailed the cause. Spray silicon based ( NOT WD-40) lubricant on the wires and engine. Helps preserve

Boot gets hot because the heat for the combustion chamber ( the absolute hottest port of the motor) is the other end of the spark plug. The engine block acts as a heat sink and the porcelain has those ribs on it to dissipate heat. But not all.

Each engine ignition coil is a constant current source (inductor) and when you open the circuit it still wants to push constant current through the air- hence the arc. Run any AC motor like a vacuum cleaner and yank the plug out of the wall. Same effect except AC cross 0 amps 120 times a second. DC never does- hence the big arc in spark plugs. And the limitation on DC circuit breakers because the huge air gap you would have to create to stop high DC currents.

I'm sure that explains what I think you're alluding to? Could the coil be putting out a stronger spark? Stronger spark would need MORE coil turns then are in there or much higher input voltage at the coil. And if the spark gets too high, the insulation in the coil would catastrophically fail (trash can).