Kohler M18 skip

[DieselDoctor]

I recently purchased a 782 that has a M18 transplant from a 1811. The engine starts easily and runs fairly well although it seems to misfire intermittently at all rpms. Not know any history other than what the PO told me "runs good" I started down the diagnose and tune road. First, a compression test. Both cylinders are between 95-98 pounds cold. New plugs of correct heat range, gapped and installed. Adjusting the carb has no effect on the misfire but I can get lean rpm drop or too rich when turning the screw. Fuel pressure is steady at 3 pounds. Old plugs show right bank is lean. Pulled manifold and replaced bad gaskets between the head and manifold. Very slight improvement - less misfire. Thinking it is fuel related I swapped carbs with a known to be good carb from the M20 in my 2072. The 782 still misfires. Put 782 carb on 2072 and it runs fine, so it's not a carb issue. I did look for cracks on manifold when I had it off. It looks good.
I have begun to suspect the ignition module/coil. I disconnected the kill wire at the plug. No help. Listening to the motor it sounds as though the timing is off. If this was a small block Chevy with a distributor, I'd turn it a little. The motor just sounds like it is laboring, and of course skipping. Can anyone think of something I've missed? In order to replace the coil, I will need to pull the motor from the chassis so as to remove the flywheel shroud. I have no problem doing this but would like to eliminate everything else. Has anyone ever experienced anything like this?