I have asked this asked this ? before & have never received a solid answer. I have a early model doug thorley header model # 542Y & what looks like the letters OC after. I have a 1993 Toyota pickup extra cab 22RE the header does not have holes on it for emission tubes, but does have cut outs on the flange on the header that look like the tubes would fit. Also very close to the header flange is a O2 sensor location, on my truck the O2 sensor is behind the catalytic converter. I'm hoping I can just block off the O2 on the header & put it behind the CAT. When looking inside the engine bay it looks tight but hopefully do-able. I'm wondering if anyone has successfully done this.