A Test For You Auto Savy Guys.

I drive a 83 Merc Marquis with 114,000 miles. I recently had a/c recharged. With car in park, or in gear with brake applied, it blows very cold and all damper doors and vents work correctly. When driving, as I depress accellerator the dash damper door will close allowing me a face full of hot air. As I let off the throttle, the doors will regain the vacuum to open and all is well. I have thoroughly been through this vacuum system checking and exploring, but this is the first time troubleshooting one. At idle, directly off the carb I have 16-18in vacuum. In gear with brake I hold a consistent 12-13in. Every vaccuum motor and line in the interior is proven to work and hold vaccuum as well as the damper door selector switch. Under the hood, I have located all the little vacuum ports, and retarders, and valves, and lines and none have leaks or defects. Air pump is pulling good air through the by pass valves and egr and hoses and all that. So why is the throttle pulling so much vaccuum away from my a/c? Would this point to the carb not producing enough vaccuum to handle climate control and the transmission? Will the carb need to be rebuilt, or can the vaccuum be boosted somehow? O yeah, transmission modulator is new also with no leaks and shifting properly. Ive also checked all the in line check valves along the way and also added a few redundant ones just to eliminate a variable here. To everyone thats sick of reading this, Ive got at least a year & 1/2 off and on straightening this out and Im running lean on nerves. Do me a favor and prove the ignorance of my ways.