SOLVED!....sort of. Where's there's spark.. there's no fire!

A mixture does not have to be stoichometric (perfect theoretical air/fuel ratio) to fire. A weak spark will idle fine then the engine will mis-perform as speed increases.

The cap looks fine in the image. Spark at the plugs cannot be there one time and not the next when verifying spark integrity.

Does the engine "sound normal" when cranking? Pulsing as individual cylinders go through their individual compression cycle?

What is the COLOR of the spark plug center electrode porcelain tower? The one inside, near the spark?