Quad, I wanted to continue this on a new thread. I do have xzt plugged in AFTER the new guage wiring. So the guage wiring is first on the rail then the XZT. I'm sorry it's been almost 2 years since I installed the XZT and I forgot it was plugged into the rail... Stupid me, how else could it increase pressure..

Anywho... I took some readings after a highway drive just now. They are still kinda freaky. I happened to have my Diablo plugged in on the obd port and noticed that at idle in park it read 47mpa which corresponds to about 6768psi while your guage was reading 4200psi...?

Here are the rest of my readings. Maybe you can set me straight...
Quad vs. Diablo (I convertered to psi from Mpa by multiplying by 144)

4800 - 7488
8600 - 11808
11000 - 14832
12000 - 15264
13000 - 16272
Seems consistantly about 3000psi difference
Now it gets interesting...
19000 - 19440
22000 - 19584

That's the most I could get while driving and writing as best I could so numbers I'm sure are off alittle, but we are seeing a pattern, aren't we. Assuming all is fine with your guage and my Diablo, what do you think this is caused by. Truck runs very, very strong. I'm probably close to or over 600rwhp in current configuration, but haven't dynoed in around a month...

 

PLug the bypass in on the XZT and then see what happens.

 

I'll give it a try and report back sir...

 

Re-installed with the XZT first on the rail and readings are still the same??? Why would the rail guage read differently? Next I'm going to try returning the Diablo to stock and see what it shows...

 

Quad, the spare wire that isn't being used (fuel pressure?) is that a black wire with ring terminal? I grounded the other black ring terminal to the dash...

 

The small terminal is for the fuel pressure sending unit and the large ring terminal is for the ground. I am not at the office so i do not have one in front of me.

Earlier I did go out and stick one on a stock 600 truck and it was reading about 6800 at idle.