The Air Door in the snorkel should be open at all times when the engine is running. The Heat Door, controlled by a TVS (not the same one that controls the EGR), should position itself to draw heated air from the exhaust manifold stove when the engine is cold, and then move so as to draw fresh air from outside once the engine warms up. When the engine is warmed up and running, you should be able to see straight through the snorkel. The delay valves cause the doors to move slowly instead of banging open or closed.