What you are seeing is what fuel mode the engine is in. During warm up, the fuel system will be in open loop. Once engine is at a minimum temperature, it goes into closed loop which all sensors are being used to calculate fuel usage etc.
If you already changed plugs, wires, rotor and cap, I'm gonna lean towards the fuel spider assembly. These injectors are notorious for leaking and causing misfires. There is an upgraded fuel injector assy for these 4.3 and 5.7 engines.