Stock everything (plugs & wires). Way back when I bought the car no miles (now 27K) I had a idle misfire issue (only happened after extended period of being idle) and was in and out of the dealership several times. They changed plugs, wires, injector and still had the same issue. It ended up being a PCM update that came out several months after I bought the car. No problems after that for a while. Then one time a while after the PCM update I did throw the code again but it cleared itself after 2 days.(?) I talked to a tech at gm and he said that the code cleared itself because the car didnt misfire anymore for so many driving cycles so the pcm cleared the code. (ok then) Well after that occasion it didnt happen again.