2000 GMC Sonoma Hesitation and sputtering

When first started up and running, my truck idles rough and hesitates very badly, along with sputtering in lower rpm ranges and during slight throttle push. When hammered down it seems to not be very bad. Check engine code reads multiple misfire and lowered injector pressure, however it goes away over time. I have replaced the spark plugs, wires, distributor cap and rotor, as well as the fuel pump and fuel filter and Problem still persists.