How many of us are there? Owners of Dodge based RV's?

The red tubing entering from the right is from the vacuum tap on the Engine. Shiny little black piece is Check Valve. Black tubing with black ZIP Tie leads to the HVAC Controls which are vacuum powered on our Ford. On your Dodge, it leads to the Cruise Control. Look carefully by the ZIP tie, and you'll see a black hose leading toward the upper left of the picture. That one goes to the...
Dorman Reservoir, where that black hose runs from the Check Valve, which is also a Tee, parallel to the bottom of the picture, behind Oil Filler, Wiring Harness and Transmission Dipstick, to the single connector on the lower left corner of the pictured Dorman reserve tank. Here's the Dorman 47150 Check Valve and the Dorman 47077 Vacuum Canister

Circuit is Source (engine intake manifold) to Check Valve. Then Check Valve to Tee. Tee Branches to Vehicle system (HVAC, Cruise) and to Reservoir. Vacuum in this little system rises to adequate on Cruising and maximum on Deceleration. Would do this without Check Valve and Reservoir in those two states, but would fall to Unacceptable on Acceleration and Climbing. Reservoir and Check Valve store vacuum up till vehicle gets back to Cruising or Deceleration.

You can use Dorman 47076 . Same Circuit except 47076 replaces Check Valve and Tee.

Extra Credit Question: Why is Reservoir labeled ACME?