taylour,
Welcome to the Stovebolt. Sometimes you can find a perceived problem, even when it doesn't exist. It is not unheard of the pull a plug wire and not see a noticeable difference.
The question is, is the engine only hitting on 4 cylinders when it is running. Dual carburetor are tricky to sync and make run...this is usually the problem until the learning curve is achieved.
If you can drive the rig down the road, you would surely know if those cylinders weren't firing.
Is this particular HEI getting the voltage it requires. This style ignition is usually strong enough to fire even a super rich fuel/air mixture.
Don't focus on the ignition, concentrate of the carburetors. Make sure the intake manifold and carb bases are tight and leak free. More help is on the way.
Stuart
