Step Daughters Car with P0304 code
 

My step daughters 05 Neon automatic with a 130k on it, has been throwing the #4 cylinder misfire code. I'm not real familiar with this engine, if it was a Ford 5.8 liter or a GM 3800 engine that's a different story. What I have done after it first threw the p0304 code was change the plugs, wires, and coil pack. It ran fine for her for about a month and the code came back last week. The injector is getting power, verified with a noid light, switched out the #1 and #4 spark plug wire, cleaned the #4 injector and swapped it to #3 cylinder. The code came back today, tomorrow I'll pull the new plug and check the gap and test the coil pack. is there anything else on these engines to check.

Thanks