Allen is right on and my question for you is, On your after market manifold,is the exhaust gas crossover ports blanked off? That helps for performance by keeping the manifold "cooler" keeping the gas dense. But in a colder climate the gas won't fully atomize. Many years ago I has a SB with a manifold that the "runners" were separated from the "valley cover", in the winter it would flood usually before it would even think about starting. My solution....I wrapped a "heat tape" around the runners and plugged it in every night. In the Spring I would remove it, although, adhesive from the aluminum duct tape that covered the heat tape was a pain to get off .