CEL on and dealer wont help

[diesel_tech2]

I have a 03 ranger 3.0L and recently had the CEL come on, went to the dealer (still under ext warranty) they told me that I got the wrong plugs, I installed the correct plugs, also installed new wires and fuel filter, drove it for 10 min and CEL came back on, called them up and they said that it needed a PCM upgrade, however they said estended warranty didn't cover it, they didn't check for anything else, anybody out there know of any possible causes that can cause this.

 

[aldive]

What was the trouble code(s) associated with the CEL?

 

[diesel_tech2]

p0304, p0305

 

[aldive]

p0304, p0305

PO303 - Cylinder 4 Misfire Detected
PO304 - Cylinder 5 Misfire Detected

Have you checked the wires?