Yup...the exhaust heat crossover passage under the carb in the intake manifold. It heats the carb base during cold driveaway. AFB's are very sensitive to this heat,and if its too hot, the fuel in the bowls will percolate out the boosters.
Also, make sure the "flapper" valve in the pass.side exhaust manifold is open when the engine is hot. If its stuck closed, it will trap heated exhaust air in the crossover passage.
