Before you go digging deep into all sorts of other solutions I would start by simply checking the voltage when it is doing the misfire issue. AND, maybe even get it in the garage with the lights off (and headlight covered over or unplugged) to see if you see spark arcing when its running poorly. Low voltage has for sure caused misfires like you mention when warmed up.
Only a slight exaggeration if it was a Ford Transit. I always demonstrated the Van de Graaff at school, for some strange reason I really enjoyed that!
My 82 Suzuki GS 1100L had 42mm cards probably not factory though, but 200 mph was as easy as twisting the throttle and was so much more manageable at high speed than my 98 Vmax. But again it had many mods to it also. But I've found the vmax at full throttle is 150 mph blur...gotta love it
