Got another quick question. I had a CEL light come on a few days ago, and it stayed on for about a day then went off. Well, it came on again this morning so I took it to Autozone to get the codes checked. I can't remember exactly what it said, but it was something like "low voltage, 1st O2 sensor". I was just wondering what might cause this. Could it be something with the wiring since I had them extended for my headers, or is it just a bad sensor that needs to be replaced? If it is the sensor, about how much do they cost?