Hey guys I have this problem. While I was driving today the check engine light came on so i decided to take it to autozone so they could tell me with their computer why the light was on, so they plugged the computer to the car and it showed that it was running lean so the guy tells me that it might be an O2 sensor so I start my car again and now the CEL is off and is not coming on again. I have an aem cai and last week I installed the tanabe exhaust do you think that might be the problem I have 2 months with the intake and never had that light on so now I don't know if i need to replace the O2 sensors. in case i have to replace the O2 sensor can somebody tell me where they are located, how many there are and about how much they cost?