I don't know if anyone has posted about these before but for you guys with headers or like me a gutted cat, these little babies work. When I gutted my cat I had check engine light come on. Never really bothered me til here lately, finally got tired of lookin at that check engine light. Bigdaddiesgarage.com sells them simply unscrew your o2 sensor, screw in the o2 simulator, screw your o2 sensor in it. No more check engine light.