I thought I would share an experience from yesterday. I had an engine “stumble “ on acceleration. It idled fine and up to 2500-3000 it was fine, any more throttle and it started shaking, missing bad. So got home and started looking, cap and rotor were fine, then I noticed around the plug wires, close to valve cover, I noticed “smoking “, I have heard it called “ ghost tracking”. It is a sign of spark leaking out of the wire to ground, instead of the plug. The higher the throttle position, the more resistance in the combustion chamber and the spark is going to take the path of least resistance. It can happen in the cap- between posts, on the rotor, on the insulator part of a plug, and plug wires. Hope you can make out what I’m describing in the pics. Usually in ignitions, it’s replacement time, no good fix. I ordered a set of wires.