420A Fuel system?

[dsun87]

i have a 255 fuel pump and a 12:1 fmu
do i really need the fmu if i have a 255????? and i have stock injectors

 

[Locke]

If you don't want to blow up your motor the first time you hit boost, you will need the FMU and the fuel pump.

The 12:1 FMU is what will be metering the extra fuel your motor needs when you get into boost.

 

[bk120]

I keep looking around for how to tune the fmu is there really any way to tune if so how?

 

[Gruff511]

You know THIS thread is 4 years old?!
But to answer your question, a 'FMU' is fixed at its specific ratio. You Can Nott tune an fmu, it only adjusts fuel pressure according to boost pressure.