On my EcoBoost engine is the 5.0 bar feed to the GDI pump mechanically controlled or electrically from the ECU? I am aware that its mechanically controlled on the test bed, but should I use the same in the car?
The fuel pressure to your Di system will only need to be controlled by a regulator. I always suggest a high quality regulator nothing cheap, as they are not particularly accurate or consistent. You can fit the regulator near the tank immediately after the pump then do the return directly back into the tank and then fit the supply line directly to the Di supply on the rail.