cylinder misfire

[poppop]

I started my van one morning and it ran terrible. The motor idled rough, but seemed to even out at higher RPM. I originally got a code of P0303.
I did a complete tune up(plugs, cap, rotor, pcv valve,air filter). This did not correct the problem. I now got codes of P0300, P0303, P0306. I checked all electical connections. The one thing I did discover is when removing plug wires one at a time while the van is running, cylinders 3 and 4 made no difference in the way the motor ran. I pulled the plugs out one at a time to se if I had any spark, of which they did. To make a long story short, I have replaced the PCM, cam sensor, crank sensor, EGR valve, both Oxygen sensors. I now get a code of P0304. I have performed compression tests, which are also fine. I have given up, can you help!!!

[asif420]

look at the coil see if the metal windings are rusty and starting to seperate if so replaice. When in this condition it will still fire but not as intended.