Did you have 02's and or exhaust temp sensors on the engine during the pulls? Others may be better at it but I have always had a hard time reading plugs in an alcohol engine. And you are right normally methanol has a broader flammability range than gasoline. you said you leaned it a little and the missfire went away, did you try and lean it more? I try and lean until the exhaust temps start to rise.
We leaned it out at max torque area till we saw no improvement, then had to add fuel back in at hi rpm for max power by reducing the secondary bypass pill. The plugs ( NGK5672=9) were easy to read, timing looked good on the ground strap, and the base metal plating was scorched about half way around, which I understand to be about right. Individual Exhaust Temps were used for base line pulls, then my car headers to get the tuneup spot on.
