I am finishing two TPI conversions and I am using the correct TPI charcaol canisters. I know where all of the hoses go except for the port labeled "AIR". I know on some GM charcoal cans this port was left open and got covered by a small plastic dust cap. Is that how the TPI cars were set up too? Or did this port actually get a hose that goes somewhere?

THanks

STeve