The black line with the white stripe is a vacuum line, currently connected to the vacuum pod that opens the recirculation door. With the climate control selector switch on "OFF" or "MAX AC", this line has vacuum applied, keeping the door closed and making the fan pull air from inside the cab. With the selector switch in any other position, this line is open to atmosphere, keeping the recirculation door open. use this line to open and close the bypass valve. simply purchase some vacuum line of the appropriate size along with a plastic T-fitting. then unplugged the line from the pod (the connection at the very left), plugged that line into one side of the T-fitting, ran a piece of fresh hose from another side of the T-fitting to that pod, and ran a length of fresh hose from the last side of the T-fitting to the valve itself.
The bypass valve, with the lines going to the heater core attached. had not yet hooked up the vacuum line to the valve. The valve could actually be installed in either direction make the vacuum hose run as short as possible.
The bypass valve completely plumbed into the system. This was a very simple task, and that it was worth the effort. you do not have an air conditioning thermometer meant to go into the ducts to tell you how cold the air was as it came out of the ducting, but based on perceived temperature differences between the air flow with the switch in "MAX AC" and "NORM AC", it feels as though the valve makes a difference.