Hey guys I am new to the forum and Hondas and I bought a 98civic ex with a full apexi cat back a cat delete (have a new cat for the car just haven't put it on) and no name headers. I was wondering if anyone knew what the part number for the oem honda rear o2 sensor was that's the one that measures cat efficiency and not a/f ratio if someone can tell me that would be good because I am not paying over 300 dollars for an oem and I know from auto classes at college that Hondas are technical and want oem o2s sometimes. Like I said if anyone can let me know that would be amazing