Can you tell us more, Ken? Do you mean backfiring? Often that can be caused by a too lean condition and that would be supported by the need to give it more gas. As for the Pertronix, I'm not a fan of those, but we'll ignore that for now.
Carburetor? Rochester B? Have you checked for intake vacuum leaks? Maybe at the carburetor to manifold? That will cause a "too lean" condition.
