Just want to review to make sure I haven’t missed anything or misunderstood.  What you are saying is that both plugs are firing, but the engine seems to be running on only one cylinder?  If so, have you figured out which cylinder is not functioning?  I know it is tough, but a video (link would be fine as well) showing the engine misbehaving would be very helpful

Have you tried grounding out one sparkplug at a time while it’s idling to see if it’s
firing on both cylinders?

rhalbert10@outlook.com wrote:

How do I do that?  Touch the sparkplug to the engine block while the engine is idling?

You have to find a way to short out the plug wire while attached
to the plug and with the engine running. If you notice a drop
of rpms when you short a plug out, you know that cylinder is
firing. Of course, that’s not to say it’s firing at higher rpms.

You could pull the rubber boots off the plug wires and hook
the plug wires back up, then you’d have easy access to ground
the plugs.