Just leave the port open and a to atmosphere on a naturally aspirated motor and set your pressure. Then at least the regulator will equalise pressure with altitude changes.
You only really need that port for blown motors to equalise the difference between manifold pressure and fuel line pressure. That manifold pressure is trying to push that fuel back into the injector and reduces the flow. The reg will deliver more pressure when on boost to ensure the injector flow rate stays the same.
Your ECU will have a MAP (Manifold Atmospheric Pressure) sensor that it will use to adjust injector flow in conjuction with TPS (Throttle Position Sensor)to deliver the right ammount of fuel for the specific load point.
I've got mine bolted to the fire wall with a liquid filled pressure guage attached. Easy to set and check the pressure.
Cheers