Search wasnt helpful, I know the FPCM in these nnbs trucks are kinda a pain for the big guys but they work for most vehicles like mine. What I'm wondering is what actually triggers the FPCM to increase the voltage to the pump to increase it from idle/cruise at 43 psi to WOT pulls at 58psi.
Also at cold start up the truck is at 58psi and once it cycles, the idle drops and psi goes back down to 43.

What I am getting to is when I am currently brake boosting, its only showing 43psi. Shouldn't I want it to be at 58psi anytime I'm in boost ( brake boosting or not )? I'm in first gear with the pedal to the floor.

Is it % of load, or throttle position, or afr? It seems since I put this new stall in, I need to lay into it for the fp to increase. Maybe the new engine/trans tune tomorrow will fix this but I'm just wondering..

 

Its based on fuel consumption and engine temp. If the engine is cold it stays at max pressure until heating up, where it drops to 43psi. From then on, it stays at that pressure until the FPCM senses more power being demanded via increased fuel flow, at which point it increases pressure again.