SB, where is this thing located? I've got the car torn apart, and have traced the tube to the passenger footwell, with no sign of a sensor. Have I not gone far enough?

On a side note, here's a vac question. Forgive me, but I'm trying to understand the heating system. When the heat is always coming out of the defrost vents, is it the defrost vac pod that is leaking, causing it to stay open, or is it a different one leaking causing its door to not function?