been running the same combo, same tune up, for six years, never an issue.. last night at the track, it started breaking up at higher rpm. I swore it was eating a spark plug . that's what it felt, and sounded like... checked everything.. I found my distributor rotor flopping around in the cap. bolts were very loose.. tightened it all up.. made a pass,, no difference.. very strange. runs great threw the burn out, and all the way threw first gear, right before I shift to second, it starts its breaking up thing, then right before high gear it comes back, and continues all the way threw to end of 1/4 mile...does this sound more like ignition break down, or running out of fuel thing...ive been checking everything, and cant find an issue.. thanks for any help.