I tried to post this thread in the DIY forum, but the site would not allow me to add images in a new post in that forum.

We recently wanted to add a fuel pressure gauge to our 05 RX8. We came up with a quick snap in solution.

Here is the result and the parts used. We found all of the parts on the internet for very little $. If you want to locate the gauge inside the passenger compartment, you could add a gauge line kit.



Parts used:
-6AN Flare Male to -6AN Female Coupler With 1/8" npt Port 6 AN Adapter Fitting B
-Z151 -6 AN Fuel Adapter Fitting to 5/16 GM Quick Connect LS W/Clip Female BLACK
-Quick Connect Fitting Male 5/16" to -6 AN Female
-Marshall Gauge 0-100 Psi Fuel / Oil Pressure Black 1.5" Diameter Liquid Filled.

To remote locate gauge:
Gauge line Kit Oil Fuel Pressure Hose - 4 AN Braided 1/8" NPT male / female

 

That's cool for testing, but for a permanent gauge the aeromotive adapter is best.

https://www.summitracing.com/parts/aei-15120