Vacuum Check Valve backwads
 

so i have a 1982 300d
is it possible to have the vacuum check valve in wrong?
the two ports that go to the firewall...does it matter wich yellow hose is on ... do the double ports do the same thing is my question

It doesn't matter which of the two ports on the firewall side you connect either of the lines to. They both function the same/are interchangeable.

Now, if your lines are all mixed up it's possible for a check valve the be installed backwards, in which case it wouldn't function as intended, but I don't understand that to be your question.