Hello to everyone here, and thanks in advance for any possible help.

I have a 99 ford ranger 3.0 flex fuel truck. symptom the truck has a small misfire.
The trucks cel came on a few weeks ago threw a p0304 code, i replaced the spark plugs nothing, I changed the wires nothing, I changed the coil pack nothing, I changed out the injector nothing. every time I did a repair i erased the code.
so finally i replaced the head, put everything back together and erased the code went out for a drive and...... same problem but know two codes p0304, and p0305.
Is there anybody out there that might be able to help me out???
I have read that it might be a bad 02 sensor, to a bad cat, or even the computer. how can i check to see if its the computer???
I also heard that it might be the camshaft position sensor and sequencer??

Help Please.

Thanks