My truck is a 2005 3500 A/T trans. It has Banks six gun w/speed loader ,Intercooler ,air horn, exhaust upgrades, air intake upgrades ,and FP150 Air Dog pump. I drove the truck with a scanner attached and a manual fuel pressure gauge to check supply fuel pressure. During the test the supply fuel pressure remains at a constant 19 psi, so I know that the pump is good and the filters are clean. The high side fuel pressure is a different story. Under light acceleration the pressure goes from 5,000psi at idle to 19,000 psi at cruising speed (40 - 80 mph) and holds all day long. Its when you load it, even slightly , the pressure drops to 4,000 psi. It drives like a car with a slipping clutch. It is also harder to start than before, turns over twice as long. So far I have replaced the fuel control actuator FCA, and also the fuel rail assembly which has a new rail pressure sensor and a rail pressure relief valve. No change as of yet, and it doesn't give any trouble codes.