Are you all ready running one step colder or are you running stock heat range? For your setup, definitely run 1 step colder than stock. If it's random misfires, I'd think plug wires would be the main thing and also put in new plugs at the same time just for cheap insurance.
I'm about positive it was a couple misfires that hurt my engine this last time. Basically it crakced the porcelain around the electrode and eventually it broke off and fell into the cylinder only to be digested partially by a valve.
Rick
