Plugs (I use NGK copper/V power) or wires/coils. A COP or extended plug wire into a well....look for carbon tracks from spark wire to ground....most noticeable at higher combustion loads (higher RPM's in NA, higher boosted in SC/turbo engines)....HV charge goes easiest path....higher combustion pressure sorta insulates spark going across plug gap....spark goes easy way....
Damp ignition can make misfires....so a damp day can make issues vs. a dry day....
Dielectric insulation of ambient air at seal level, standard pressure, is a lot lower than high compression/high load NA or "force fed"..
Physics son.....physics.....