it's not the vents in the Vintage that restrict the air-flow, it is the under sized fan blower because of the all in one compact unit.. I recently R&R'd a 1995 4runner Blower for a buddy and the blower fan in that truck is 2-3 times the size of the Vintage Air, and the truck has about 1/3 smaller passenger compartment size vs. the '39. That thing will blow you out of your seat. the Vintage Air systems I've seen put out about as much air as my daughters hamster when it runs on it's wheel.