The thing to do is to perform some tests with a Mityvac.

You do this by exposing the set of changover valves where you can access all the pods via vacuum lines.

The changeover valves are sitting just to the right of the CCU. You access them by removing the carpet and kickpanel on the right side and pulling the piece off the transmission tunnel. It will just barely slip out of the console.

You can unscrew the manifold with all the valves attached for easy access.

Now you can attempt to pump up each pod and see if it operates properly (holds vacuum). You can also test the changeover valves if you T into the output line (run the engine and the CCU to do it).

Why guess when an hour's worth of testing will tell you what you have.

And, there is something unique about the center vents. I had put vacuum to the center vents all the time and chose to regulate the vents via the console controls. Bad move. Those vents will never provide full heated air. They get air from a point before the heat exchanger, apparently, because they will freeze you out in the winter, even with the dash controls closed.