can the low pressure 255lph support up to 20psi of boost? Higher than 20psi?
why should I get the high pressure?

 

With that much boost your gonna have to run larger injectors, that will not require as much fuel pressure, therefore not requiring the higher pressure pump.

 

The two pumps are identical with one exception:

the low pressure pump has a pressure relief valve in the pump
housing, set to about 75 psi.

So as long as you don't set your base fuel pressure (engine off)
above 50 psi or so and use a 1:1 regulator (standard type, no rising rate)
you'll be fine if you stay at or below 20 psi of boost.

Basically its base fuel pressure plus boost must be less than 75 psi...
for the low pressure pump.


Again other than the relief valve the two pumps are identical.

Another note: you must also realize that with increased pressure the pump
will flow less, so getting the high pressure pump you can run 100 psi
of fuel pressure is short sided because you may not get the VOLUME you
need to feed your engine.

Jeffrey Atwood