I DID do a search first... Heater works great up to around 2500 rpm or around 50mph, but then blows cold air. When I pull over for a moment heat comes back. Blower continues to work. HELP
Monovalve appears ok. Vacuum?

__________________
Mr Goodfahrt (pronounced FAIRT... means "good trip" in German)

1982 300D Turbo Pastel Gray (off-white) 200k+(?)
newbie but willing