On my '83, I removed the big plastic cover that contains the floor vents. I had always wondered why neither heat nor cold came through those vents. It was because the vent tubes coming down actually dead-ended right into the fiber insulation on that cover piece. You could see the circle marks on the insulation, it was blocked air tight). I looked and looked at it and it looked like it was intended to be that way. But it was blocking the air from coming down, and also blocking the air from going into the door. Both sides were like this. I finally decided it just made no sense, so I took a hole saw and drilled out that part of the inside of the cover piece, about the size of a doorknob hole. Now it works perfect....I think. Have I done something stupid? Why was it blocked off that way?