i'm in the process of tracking down a vacuum leak so my car will shut off and my doowr will lock....so far i've determined that the leak is coming from somewhere inside the car....i've noticed a hissing sound coming from behind the push button panel for the heater in my 82 300D...at first i didn't think this was related to my doors not locking because it has been doing this for weeks....

so i took off the panel,, started the car,,, and tracked down the hiss to something that i think was refered to as a "pod"....when i stuck my finger over this the center vents came on... So should I plug this and see what happens???? would this cause my transmission to shift hard too, as it does now....