Coming off the fuel rail, I want to install a fuel pressure gauge, that will go inline with my braided fuel line going the the fuel solinoid. I know the gauge is 1/8 pipe, And my nitrous kit is a TNT F1, so I think that the braided fuel line is 4an. HELP.

 

I've done this, its stupid easy, I'm not quite understanding how you've got your kit hooked up but if you've got the stock capped fuel port, all you do is remove the cover and use a gut remover just like a valve stem in a car tire, take that out put your line on going to the guage and your all set! and yeah its a 4 an line,

 

I understand that, but I have my fuel line coming off that, going to the fuel soliniod. Somewhere in the middle of that line, before the solinoid, I want to install my Autometer fuel pressure gauge. The closer to the fuel rail, the better.

 

you'll need a 4an T fitting and a 4an coupler(double female), and thats it, as long as you allready have the extra line for the guage!

 

electric or mechanical?

if mechanical gauge, then you will need the AN T fitting. then the line, then a -4 to 1/8" adapter.

HOWEVER, i think you sound like you are wiring an electric gauge, where you only need a Single Hole Purge/Gauge Adaptors