Hello,

Been banging my head on this one for awhile. Installed 350 tpi in a cj7 all stock. In closed loop it back fires through the exhaust at certain rpms. I ran datamaster and all logs look good. open loop runs great. O2 is heated and installed about 12" past collector. Can this be to far? The values I see from o2 are swinging from 50 to 900mv. All smog removed in chip as well as engine. EGR still on. Thought the egr solenoid was the problem. Changed that same thing.Blocked off egr samething. injectors all ohm out at 16 ohms tps,cts, mat and iac all check good. Tried 2 different ICMs 2 different ecms. 2 different proms with pretty much same tune. I am about to lose my mind. Main question is does anyone know if distance of o2 from header can be an issue closed loop runs perfect. Thanks in advance.