[timsullivan]

I'm currently running the Duraspark module with an MSD distributor.

For lower rpm problems I'd also recheck the ignition timing and carb mixture screws. My guess is that the problem may be the former. I'd also check the plug wire and coil wiring connections.

I had problems with rotor phasing in my MSD distributor that required me to get an adjustable rotor with a movable rotor pin, from MSD but my problem was higher RPM operation, above 3,000 so I suspect that isn't the issue with your car.