Just a general observation for anybody chasing a misfire or stutter. During my investigation I cleaned my carbs, replaced my plugs, replaced fuel filter, cut back my ignition leads did a carb balance none of which did anything. My symptoms only came to light after riding the bike hard for a few miles and then she would misfire on hard throttle at low revs. I would recommend anybody who has a misfire symptom to replace the plug caps. You can get 4 NGK replacements for less than a tenner.
Another possible red herring symptom is a rough idle. I have a K+N filter and a Beowolf end can with baffle in. Even after doing all of the above my bike still doesn't idle smoothly but rides great so I'm not worrying about it.