Carbon build up is mainly from heat, or lack of it. By running the engine hard, you get lots more heat in the cylinders, which in turn burns the carbon deposits into ash allowing them to exit the cylinder. If this engine was leaned out a bit, the build up would probably go away since lean-burn engines run hot. A hotter range plug would also help, not so much on how it runs, but just keeping the plugs cleaner. Even a hotter thermostat can help if the engine never really get hot putting around town.
The miss can come from carbon heating up and acting like a glow plug, lighting off the mixture before its suppose to fire. Ping or detonation is a common problem with carbon build up.
Joe
