Sounds like you have narrowed it down to an ignition problem. First, I would drill a 3/8" hole in the cap inline from plug 1 to coil lead. Use a timing light to verify rotor phasing. I suspect it is off and spark is jumping to the next cylinder in line. If it does show OK, an easy patch would be wire up a timing retard to kick in just above launch rpm and crank up your base timing to get it up on the chip. To be safe, pull out the same amount to the retard module, that you are adding to base timing.