I don't know what N/A refers to. I was looking for a description of the fuel delivery system to see if the regulator is external or internal to the pump - I couldn't find the description, so I'm assuming that it's part of the pump similar to other returnless configurations I'm familiar with. If you're changing the configuration to one with an external regulator and an external return, you'll probably need to change the pump as well and then add a return line inlet to the tank. At the other end, you'll need a fuel rail that will accept the 2 lines or find a fuel rail with a built in regulator. Whether you attach a vacuum line to the external regulator depends on what it needs to control "load" or demand conditions - installation instructions should tell you this. You should do some research and determine how the stock system fulfills this task to make sure you don't end up with a conflicting control.Yes, I understand this.
I'm going to be turboed and need to turn my returnless fuel rail into return one. I'm putting an adjustable FPR for this. But a few days my car will drive N/A before I come to place where my ECU programmer lives. Should I connect a vacuum hose that goes to the regulator to the intake manifold or not when my car is N/A?