Well I had a shop install me headers and they did a horrible job, from what I can tell and the other mechanic I had look at my car the idiots that did the work on my car extended the O2 sensor wires which was correct but they have a whole bunch of different wires and they cut them in about four different places and just wraped them with electrical tape and from what i found out the many cut in the wires are causeing the sensors to have low voltage which is causing the check engine light to stay on and the car run below its performance level. So if any else has the wires extended make sure its like one cut and not like 40.