AC fog, black plastic foam, no heat?

Strangest thing happened today - I was driving along in the rain, I had the AC on low, and it started blowing fog out the AC vents. Only visible 3-4 inches away from the vents, dissipated as it went farther. Not really a problem per se, I don't think, but passengers may think it's a bit weird if that happens again... they're already a bit wary of the engine blowing up as I stare at the oil pressure gauge constantly (recent head gasket failure -> low oil pressure -> etc)

Possibly related things: It's been coughing up what looks like pieces of black foam every once in a while, some sort of cabin air filter that disintegrated deep within the dashboard maybe? And my heat knob doesn't turn the heat on - it's Florida, it hasn't bothered me too much yet.

Vapor is just the right mix of cooled and humid air -- like when you open your refrigerator freezer door on a humid day.

Foam is probably filter over the A/C evaporator coil. I don't know how important this is or how dificult to replace.

No heat is likely the vacuum valve just in front of the passenger side firewall where four heater hoses come together. Assuming vacuum is present, the valve is probably corroded or leaking. I replaced mine several years ago ('85 XJ) -- $50 at Autozone.