FPR sets the BASE rail pressure.... usually in the low 40's psi. it is 1:1, as is the one you linked. that one is adjustable- meaning you can set base pressure say, 50 psi.
and FMU, RAISES in ADDITION to the FPR 12 psi of fuel pressure for each psi of boost it sees through its vacuum line (in a 12:1 fmu).
so if you are running 6 psi off a 12:1 fmu and the stock fpr-
you have 42 psi in the rail at idle/out of boost.
a 1 psi you have 54
at 2 psi you have 66
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the key thing to remember, is that PRESSURE is NOT VOLUME. and that's why fmu's are only good up to say, 6-8 psi on a medium t3/t04e turbo, and 10 on a smaller t25
the fuel pump is mutually exclusive.
basically, if your rail is calling for 100+ psi, your stock pump simply can't deleiver it fast enough- and thats where the inline booster comes into play.
it raises PRESSURE once again, and again, is only good to a certain point.
the INTANK pumps, actually FLOW MORE VOLUME (litres per hour).
to sum up- here's what you need, one of the following:
- 12:1 fmu, missing link/map bypass check valves, stock injectors (310s are know to work, but push it a little bit... so, stock 240cc-310cc is the range), inline pump booster
- no fmu, no missing link, vafc, intank pump (preferred- but an inline MAY get you by), and 440 injectors in "hack" formation
- no fmu, no missing link, no vafc, hondata/uberdata/aem/etc, larger injectors sized to application, intank pump
with either of those setups, the stock FPR is fine. I am running the stock one.
But, if you need a HAIR more fuel, a FPR can aid in giving you a slightly higher base pressure, and thus, overall more fuel throughout the rpm band.
but again, remember, PRESSURE IS NOT VOLUME.
so to sum up the differences-
FPR sets the base rail pressure.
FMU ADDS to the base rail pressure in ratio (12:1) for each pound of boost it sees.
to take that a step further, running high rail pressure, caused by the fmu, requires fuel to actually BE THERE in the first place. cuz you can't feed the motor what hasn't been brought up from the tank, through the filter, and into the rail- and that's where your inline booster and intank pumps come into play.
clear now?