I have 2 Pontiac Montana's an 01 and an 05 the 05 has a problem when it's cold I can drive it and it runs great plenty of power but as soon as it's warmed up it has no pick up and go power tried a new filter no difference, tried putting in a new fuel pressure regulator no difference so changed the map sensor, throttle position sensor and the idle speed solenoid, new plugs nothing works, the only thing left is to replace the fuel pump! Any ideas?