Time to do the dash flapper door
 

Being that my inner heater / AC unit is stuck in the defrost mode,.I will be pulling the dash to fix it,Iam curious if there is a well known product to repair the door, I have seen the tape sealing method,just wondering if there is a newer stronger foam to cover the door after it's taped off. Thank's Frank:

I applied aluminum tape to both sides, then used Barge cement to adhere very thin neoprene sheets to both sides. I didn’t trim the bottom main flap enough so it’ll squeak a little on power-up. Otherwise has held well.

I just did the "address the grey foam issue" fix recently following the guides put forth on this site. I used Gorilla's 4 in wide "Patch & Seal Tape" product. It has backer material on it to keep the roll from sticking to everything while you contort your arm into the hole. So I cut the tape to length (and width as needed, since it's so wide), removed a piece of the backer material, got the tape set just right on the little metal door, and striped the backer material to finish applying the tape. I also poked little holes all through the patch tape in case having some diffusivity was helpful (since Porsche went with foam themselves rather than a solid piece of aluminum).