Have a look at these plugs

Lower right and left, upper left and one below have fouled at some time.

Fouled plugs may not always clean themselves. The fouling destroys the insulating properties, and results in weak or no spark. You might try changing plugs, check the plug cable resistances, check other ignition components. Verify timing. Check spark intensity with adjustable visible spark test on each cylinder.

I find that on a well tuned engine the plugs remain clean, regardless of how it is driven.

AFR can give wrong readings if the sensor is polluted by extremely rich mixtures.

Tuning an engine under load at wide open throttle involves setting table values at each RPM cell for maximum MAP. Not sure how all that is done on Fast.

Miss fire means significant problems in ignition or fuel mixture. I find engines have significant toleration to both timing and fuel mixture offsets, and still run not too bad from drivers seat. The missing means something is off, timing several degrees or more, fuel 10% or more off.