I have a DC 4-2-1 header on my 96 teg and it has no o2 sensor and I have a hi/flo cat that doesn't have an o2 sensor either. So yea I don't have an o2 sensor I guess. The owner before me put in an A/F ratio gauge and when I got the car I wondered why it did not work. But now I know I don't have one I guess? I'm figuring he got the gauge before he bought an aftermarket cat. Is there any way I could hook this gauge back up to something? I hate the fact that it is useless to me right now