It had single exhaust before,so only 1 sensor. I didn't put cats back on either since I don't have emissions where I live. Do I need a sensor for both sides and cats?
Both of my exhaust manifolds were cracked so I replaced them with a set of Headman long tube headers with 2.5" dual exhaust. I did not install cats but I did put mufflers on as I can't stand straight pipes. This is on an 89 4wd v1500 Suburban. The headers didn't have a bung for the o2 sensor, so...