So I'm knee deep in the evaporator core replacement in my 95 e320 wagon. we've made amazing progress and are already on the puttin' stuff back phase on the second day of work (maybe 8-10 hrs so far.)

anyway from what i read just getting run of the mill weatherstripping from home depot is all I need to seal the interface between the box and the firewall correct? scrape off all that grey putty.

is it okay to use silicone rubber to seal up the blower motor box?

what about the flap that I guess diverts between AC and heater. you know the one, the one that is coated with some kinda of foam insulation. the blower motor side is pretty rough, the other side looks really good. what about scraping all that junk off? bad idea? what is that foam for? what about replacing it with whatever adhesive-backed insulation/foam I find?

The run of the mill HD weatherstripping is fine. That's what I used on my 124 wagon. I didn't bother to remove the factory goop, just left it in place. Guess it depends on how OCD you are.

The black foam on the flaps was there to insure the flap completely sealed and didn't leak air when closed. At this point it's quite brittle and not very effective. Your best bet is to remove it. Otherwise it flakes off and flies out the vent in small pieces, landing on your spouse's clothes, with predictable results.

Don't understand your blower box question?

- JimY

I went ahead and removed all the gross foam. the other side of the flap though looks perfectly fine so I left it.

Regarding the box. what I was talking about is the grove between the top half and the bottom half. I filled it with silicone to further seal the box.

BTW I am way OCD and removed all the grey nasty putty and left it sparkling clean.