You may want to try a different brand of spark plug as sometimes a specific brand of plug cannot handle the dynamic compression.
I use to work for a gas station having an AC Spark plug cleaner using liquid sandblast and fresh water rinse. Remember the blue machine?
After cleaning, you would screw the plug into a fitting which was pressurized with shop air and attach a plug wire onto it. Hit the button to fire the plug, see the reflection of the spark in the mirror and turn up the air pressure in the chamber to see when the plug would misfire. If the air regulator knob could not be turned out of the red zone, bad plug.
I use Autolite, but, everybody is partial to a brand of their choice. Champions and AC's misfired, but, Autolite always works for me.
Everett "OBJECTS IN THE MIRROR DISAPPEAR UPON RAPID ACCELERATION"