I changed my head gaskets and all the gaskets on the top of the motor. It runs but idles rough and it is throwing codes for misfires at 3&4. I put new plugs wires cap and button in. I have spark fuel and compression. What else could it be?

What plugs? Might wanna recheck firing order. I have screwed that up in the past. (yes, even after checking it three times.......)

I put NGK spark plugs in it. I would upload a picture but it is not letting me.

Best to host pics elsewhere, and then just use bb code to embed them.

NGK copper plugs? These trucks don't like the rare earth fellers.

the box says iridium on it. I will get some copper plugs and hopefully that will solve the problem.
I tried champion copper plugs. The misfires are still there and now I have codes for the injector circuit on 3&4 also. Would that be in the wiring somewhere?