You are not listening.
The contraption was a rig to alter the original simple hydraulic system and allow an electronic correction. It was similar to adjusting the fuel mixture with a ten pound sledge hammer.
The device is a BY-PASS a RIG, it is not involved in the normal operation of the simple K-jet fuel system. The warm-up/control pressure is a separate fuel pressure control system, it has its own return line (see warm-up regulator..."In" is from the fuel distributer center top, out is from the other fitting back to the fuel return. The device I describe is attached to the "In" and dumps to the out, diverting fuel around the regulator.
If the car was running with that system recently you will need a significant fuel mixture correction once the system is restored (plugged/eliminated).
Bosch Master, ASE Master, L1
33 years MB technician