The FPR is usually quite reliable. The most common failure is the internal diaphragm breaks allowing fuel to get to the (supposed to be) closed vacuum side.
The hose attached to the Cold Start Injector uses a clamp (unlike at the fuel rail). So it is relatively easy to remove the hose there and tee in a gauge. Too much or too little fuel pressure will prevent the engine from running properly.
Yes, cool pic!
Does the fuel pressure gage actually have to be t'd in? Can it just be plugged into the end of the hose when its pulled off the csi, realizing the csi won't be able to spray, so perhaps doing it when the engine is warmed up?