UPDATE: Just last week I was cleaning out the last of the falling leaf debris, getting ready for winter, when I noticed a squareish rubber plug with 2 nipples on it, laying loose by the fender and the battery. Not having any idea where this thing came from, got me to looking. Turns out both ends of the firewall, up top by the black windshield wiper trough have these flapper type vents, like the type in the back of cab. The passenger side fell out, thats what was laying by the fender. With a mechanic mirror and a light could see where this thing goes. Reason it FELL off is, holes are too big, or nipples are too small,or both. Was fun trying to get these nipples back in the holes blind. ONLY TO HAVE IT FALL RIGHT BACK OUT. Some silicone adhesive fixed that. Now with that rubber plug out, the whole mouse family could dance the jig as they went through there. I KNEW there had to be a way people were getting those mulch piles on top of their cabin air filters. I found mine, yous may vary.