Here's a place to buy the diaphrams and tools for the actuators....along with some interesting and inexpensive solutions for other problems.
http://www.autoluxmbz.com/
Can someone post directions for getting to the actuator which controls the center vent? If it's a nightmare to get to I may just fix the vent in an "always open" position. BTW, I'll be replacing the radio shortly so this may be a good time to attempt the actuator/vacuum troubleshooting.