so everything was fine until you replaced the coil ? was that just for preventive maintenance that you changed the coil ? could be a poor connection or a lower output coil that doesn't have the juice to keep the spark strong under high output demands. seems doubtful but you could put the old one back in and see if it makes a difference. also on mine, the wire came loose inside the distributor cap (I think thats where the one side goes to from the coil). doublecheck that. i tried 93 octane and it didn't help my issue, next up retard timing from 12 to 10 BTDC.