One other thing I did was replace the door that was on the original plenum. The original plenum was made of a thick paper fiber material and I had bought a plastic one to replace it several years ago. This black door can open and close to control the flow of air. I had to cut an opening in the side of the plenum and pop rivet the door in place. I don't know if it will ever come in handy but it didn't cost anything and only took a short time to complete. Next –––>