Ok, so I'm here to follow up with my results. I pulled everything apart, and pulled the passenger seat out for more room. Pulled everything apart, as well as pulled out the blower fan to clean debris out. Not too much in the blower motor though, which is good. I took a look at the flapper door when I turned the knob. I could see it move, and hear it close... Crap: Nothing wrong with the flapper door. So I started to put it all back together, but something told me to try once more with a mirror or something to see behind it. sure enough, there was something like a rats nest behind it keeping it from closing all the way. YAY! Now she closes all the way! There were only two 5.5 MM screws holding the cover on,for anyone's future reference. It was 10x easier with the front seat removed by the way. Thanks Gary for the help!