Well, without the caps you'd have a path for air flow through the flaps. Did you remove the caps? Does it look like there were caps at some point? Just trying to solve the early Barracuda ventilation mystery. I'm starting to think that maybe air flow was too much of a good thing with the early cars, and the factory changed the design to make the flow controllable by having removeable plugs. My car had evidence of duct tape partially covering some of the rear vent rectangles. Hmm, what was that for?