ok I am new but hear me out. I have headers and uppipe and the front o2 sensor will not screw in properly due to oversizing of the up pipe. evedently the o2 sensor tip rests against the piping? does this make sense? Anyways I had this done when i replaced my motor... another story... Damn oil pump! they told me this so the front o2 sensor is not in and plugged. I have the access port and i am assuming this is why i am not getting air fuel ratio. What can i do to fix this? Are there aftermarket o2 sensors? do i just weld the thing in there? most importantly will this screw up my car. The thing runs like a bat out of hell.