Possible warm air diverter that cause warm air to be sucked up from a pipe that is connected to a can or housing around the exhaust manifold. The warm air is fed into the air cleaner to prevent carb icing in cold weather. When the engine coolant warms up enough, it shuts off the vacuum, the diverter closes and the warm air ceases to be fed to the air cleaner. The carb manifold has coolant passages that deliver hot engine coolant to the carb base to prevent carb icing. It only well with an engine that has come up to operating temperature. That's why the warm air is pulled up from around the exhaust manifold when the engine is cold.