I have a pressure gauge that has a 1/8th fitting, what size does the fuel rail take? so I can run a line so I can tune my motor.

Do you mean a 1/8 NPT?

The threads you see after you remove the pressure port dust cap is a -4AN. There is some debate whether this is a real -4AN configuration or not.

If you mean what size threads is the pressure port to fuel rail, I don't know but it's definitelty NOT a NPT thread. It's a straight thread that seals to the rail with an aluminum washer.

You'll need a hose that has -4AN fittings (female) on both ends so you can hook up to the pressure port fitting (you'll need to remove the Scharader valve from the inside of the pressure port first). You'll need an adapter that will adapt the other end of the hose to your gauge; a -4AN male to 1/8 NPT (male/female depending on your gauge).

Autometer sells a gauge hook up kit with the hose and adapter fittings.

http://www.autometer.com/cat_accesso...st.aspx?pid=18

Note: AN fittings are not the same as the flared fittings you get at the hardware store.

the schraeder valve is -4AN. But you need to remove the core from it. The exact same thing a tire valve has... You need to get -4AN male to 1/8th NPT female...

The link that you gave to autometer... None of those packages have a female -4AN fitting in them....
I know Accel sells a kit if you like to pay a lot....
http://www.jegs.com/i/DFI/310/74726/10002/-1
I'm in the same boat, I'm looking for a -4AN female connector so I can hook up this gauge (with the 1/8th male fitting) I bought.