I HAVE 90HP INJRCTORS WITH A 150 FASS SYSTEM .... WHAT GAUGE IS BEST FOR ME?

 

You should really get both but if you have to choose get the Rail pressure.

 

Fuel pressure is what the Fass puts out. Rail pressure is what's sent to the injectors. Probably knew, but in case a new member should happen to peek at this thread.

 

You have efi live, you can use the scan tool to monitor the fuel rail pressure when tuning and logging and when you have your tune set you really wouldnt need to look at it untilll soething funny happens

i would reccomend a fuel pressure gauge inbewteen the fuel filter and cp3 to make sure the cp3 stays happy, and make certian that its not the fuel pressure from the lift pump not causing issues with rail pressure.