Well as I described, the fuel pressure just slowly fades away as the car is being driven or sits and idles. Either the mechanical fuel pump is bad of the fuel pump in the sump is getting hot. I think.
If not already done, the pump can be slowed down at idle and low speeds to prevent overheating; read the part about PWM in the link below.
https://fitechefi.com/faq/fuel-pump-control/I do not believe the vent on the FCC is intended to be a return line under normal conditions, it vents vapors and act as a relief if the internal float fails to shut off fuel flow. I've never seen fuel flow from my vent.
