Hmmm, are you sure about that? I don't know myself how they operate for sure. But I can tell you that with out any vacuum lines hooked the doors in the snorkels are wide open.
Time for me to eat some crow......The evap shutter that I was reffering to might not even be a Mopar dealio: If the vacuum pots are directly over some preheater ports under the snorkle, they are called "heated air diaphragms" or other manufacturer name. They are used with a thermo switch to pass or block a vacuum signal to the pots. If the car is cold, the thermo switch is open and manifold vacuum is allowed to close the shutter, diverting intake air from the preheater hose thats coming from the hot exhaust manifolds. When it gets warm, the vacuum is weened off, allowing the pot to relax and open the valve to fresh cool snorkle air. If you disconnect the vacuum hoses, the relaxed diaphragms will be open to cold snorkle air, my bad. On my truck, this is a bimetal spring function, and my evap shutter (looks just like the Mopar single snorkle air cleaner part) is between the preheater hose inlet and the air filter, closes when I shut the motor down, ie. no vacuum. It doesnt shut down during WOT as the spring action is very light. Supposed to stop a carb fuel bowl from evaporating, a closed system...OOPS!