ddgonzal
I wonder if you are also suffering from carburettor ice. High humidity, low temp,... could be. When the engine warms up, & i assume that your air filter hot air system is working, the warm air melts the ice in the internal air passages & it runs better.

IF that is the problem, then i found that running the car for a few minutes before moving off is enough to provide warm air from the exhaust manifold. IF there is ice in the air passages, the carb runs rich & gives you poor mileage & bad running.
Yes, i know about the ignition, & this is a good thing, but just keep the carb situation in mind, as it is possible that you have two diferent problems at the same time.