W124. (Answer now found and posted below as the first reply)

I've changed out the innards to my hvac pods. I've tested them but on one (#4, the center flap) which is the one in the center where all the aluminum fins are, is weird. It won't "hold a vacuum" by way of the numbers on the gauge of my handheld vac pump, but the rubbery part on the bottom of the pod gets sucked into the pod. So it has to be getting vacuum, yet it doesn't register on the pump gauge.

I wonder if that's the way it's supposed to be?

Ok, I found out that yes, the pod is working right. It must be such a low amount of vacuum needed that it doesn't show up on the hand pump gauge when the pod is out. I'm sure it'd show some suction when hooked up to the car because then it has to open and close a flap so that would need more power to do that. But out of the car, nothing shows up at least not on my gauge (gauge is working) yet the rubbery bottom of the pod gets sucked in.

Got it all working fine!