At wits end......

Yes, explain breaking up. The fuel starv/lean bog is a total lack of power, like the heads just came off and a low deceleration fart out the headers. Ignition would be a crackle and pulsation of power, bit time missing. If it refuses to go past 3000 rpm floored but with no snap,crackle and pop its probably fuel related or timing but that would slso show on idle.
My old 2 stroke yamaha was famous for fouling plugs at the worst times, ie in the middle of death valley when i was already 1/4 mile behind the riding pack. Had to remove plug and clean it with a wire brush. Took about 5 minutes and always burned my gloves. That was classic fuel starve/lean out as there was nothing in the cylinder spark wise, same as nothing in the cylinder fuel wise. Wouldnt happen in V8 as there are 7 more plugs.