912ULS MAG DROP

It may be trigger coil faulty, check trigger coil or Trigger coil gap issue.

 trigger coil air gap .020"

Gap  greater than .035". It will stop firing or MAG drop. Check it and tell again.

'Stay home and say thank you

That much of a drop might indicate you are running on 3 cylinders and the bad A plug is in a different cylinder than the B.

Look at your EGT temps to identify the culprit.

If you do not have EGT's try an IR temp gun, or just start it on one mag at a time for 10 seconds and see which exhaust pipe stays cold.