One hot mother!!! Be careful in your garage!!!!!!!!!!!

I'm a "trouble shooter" type of guy. If it was me I get some of that "foil tape" and stick a small piece to the vent (near the most heat) and see what happens. All this on a cold day when the heater is running (during the day when you can watch it). If it burns and smokes your problem should be absolutely solved so you can sleep at night. I know that I wouldn't sleep well at night if I didn't know what caused the problem. If your happy with what you have already found then the case is closed???