[olddog]

Although I never adjusted a carb with a wide band, that seems way too big of a change for a 1/16th of a turn.

If the O2 senses no change when it is breaking up, that would tend to indicate that the fuel is getting burned.

If there was a cross fire and a cylinder fired at the wrong time, the fuel would get burned, but the engine would miss.

If there was a valve issue such as float, the fuel would burn, but the engine may seem to miss if the float was only on one cylinder.

Thought to consider: Are you experiencing pre-ignition. A high compression engine with a big cam has a low dynamic compression at idle. At high rpm the dynamic compression goes much higher. Is your dynamic compression going high enough that the fuel is lighting before the spark. Fuel lighting too soon kills power because it is preventing the piston from coming up. It may seem like a miss-fire.

I hate running a cold engine hard, but would it break up on a cold morning with a cold engine?

PS
Do you have an O2 on each bank? Or is both banks going into one pipe? If the O2 is on one bank, it may mean that the cylinder that is breaking up is on the other bank.