Diverters for heater core box

This is probably a question for someone who has worked in a VW shop. I'm replacing the A/C evaporator in my 91 Jetta GL 1.8L. I've removed the dash and the heater box. The heat didn't work very well and the fresh air vent brought in fairly warm air. I'm certain that the reason is the dirverters (or blades, mixture controllers, or whatever they are called) inside the box. They are thin sheet metal with holes in them and control the air flow. I can tell that at one time there was foam rubber on them (some was still left). My problem is that I've never seen what one looks like that is new. Is the entire surface supposed to be covered with foam rubber? How thick was the foam originally? Is the foam closed pore like a wet suit or open pore like the filter in a window A/C unit? Are both sides of the metal supposed to be covered or just one side?
Any help will be appreciated. :feedback: