man did I miss this one .
I'm saving a Subaru SVX aux air regulator on a vanagon sometime.
The aux air regulator's  only purpose is to add more air around the
throttle plate for faster cold idle.
I don't even get the impression they are working that much often.
The engine can run fine with this part not doing much .

just about any kind will work.
They have a temperature sensitive  spring that opens a valve in it when
cold.
then power to it heats it so it closes after a little while.