I don't know of a way to test it.
Where I found my info to try it was this link.
https://forum.supraboats.com/archive...hp/t-1005.html

I have the gauge to try to determine where another issue lies. (Bog/dieing on wide open takeoff, but ease into throttle works).
It will show me if there is enough fuel pressure throughout the RPM range.
If not, then I will replace the fuel filter, retest and then look at the fuel regulator, then fuel pump.
The schrader valve is located under the black plastic cover over your flame arrestor.
Follow the fuel line off the front of the throttle body toward the fuel pump on the starboard side, you will see a black screw cap.
Unscrew that and you will see a tire pressure looking valve.
The gauge I bought ($40) screws onto that and will allow you to monitor the pressure as needed.