Fuel pressure problem-guages read off!

[turbovanman²]

This is weird and don't remember this every being an issue before but, I just installed a fuel guage under the hood-to aid in adjusting fuel pressure at the track. It's teed in before the reg. Get it all hooked up and then hook up my other guage at the fuel rail, this is the interesting part-with the AFPR hooked up, both guages read the same-unhook AFPR and the fuel rail guage reads higher???????? WTF is going on, I know I have checked fuel pressure before on tons of other vehicles before the reg and NEVER had an issue.

[Tony Hanna]

That is strange. Since a liquid can't be compressed, I'd think that the pressure reading would be the same anywhere between the pump and the regulator on the feed line.
Allmost sounds to me like the gauge you teed in is hanging.

[turbovanman²]

Maybe but then it wouldn't read properly when I hooked up the vac line??????????

[Tony Hanna]

Maybe but then it wouldn't read properly when I hooked up the vac line??????????

Well, it's reading lower with the vac line hooked up right? Maybe whatever is hanging the gauge is doing it at a certain point in it's sweep. I see this alot at work on oxygen and acetylene gauges. Some of them will read fine up to a point but won't pass that point. Often a tap on the gauge will send the needle to where it should be. An example of this would be an oxygen gauge that will go to 0 with nothing on it, but won't go past 1200 even with a fresh bottle. Give that same gauge a tap and with the new bottle it jumps to 2000 psi.
I'm not saying this is the case in your situation, just that it's something to consider. If you have access to another gauge, it'd be worth a shot to swap it in and see if there's a difference in how it reads.
HTH,