So my 2000 ranger 3.0 flex fuel will start and run fine for about 15 minutes, then starts loosing fuel pressure only when under a load. You can push the clutch in and give it gas and the fuel pressure won't move. I put a fuel pressure gauge on it while diving and its stays between 50-60psi until it starts acting up, then will slowly drop down to 20psi and starts to backfire. At that point if you shutdown and restart fuel pressure will go back to 50-60, until about 15 minutes of driving and it starts dropping again. I've replaced crank sensor and camshaft position sensor and also newer fuel pump.I am stumped. Any help greatly appreciated