How do you have the gauge between the pump and regulator “at the carb”?

The gauge to check the pump pressure should be mounted “before” the regulator.

Pressure should be set with a small amount of fuel flowing through the regulator(a small ball valve works good here).

If you’re running a bypass regulator, you may need to block the return to set the pump pressure.

Personally, I wouldn’t be running a bypass regulator with a pump that can only generate 12psi.