Last post series deleted.
My last this subject. Delete if you like.
Subject is the switchover valve black line to the side VCV three way to black line into the passenger compartment.
The black line three way into the passenger compartment is a VENT.
Connects to NOTHING. Same as a vacuum LEAK.
Measured 5 inches vacuum to the VCV with the vent disconnected and plugged at 2000 rpm. Zero inches vent CONNECTED per MB same rpm which isn't enough to acuate the side VCV.
I suspected a vac leak engine switchover valve on top of valve cover.
126k miles and 1983 CDT.
Replaced with new switchover valves and got 15 inches with vent disconnected and plugged.
5 inches 2000 rpm with the vent connected per MB. Sweet shifts.
The tranny was overhauled two months ago. Goodshift SD and good shift performance improved significantly by R/R the switchover valves.
EOP

Get rid of the switchover valves, they're useless. More than likely, you just have a worn out VCV thats leaking or simply needs adjustment.