[Dukedesmo]

If the pressure regulator is in the tank, then it shouldn't matter which way round as the fuel is pumped in a loop with the regulator controlling the pressure in the loop - it matters not which injector is first in the loop as the pressure will be constant/equal anyway.

My 916 has such an arrangement and the lines are marked 'M' (Mandata) for the flow and 'R' (Ritorno) for the return but it will work either way, just that due to the angles and space constraints they fit better if you follow the labels.

If the regulator is in the line/near the injectors then it would matter as the loop is now directional due to the position of the regulator.