Hello everyone, this is my first post on this site, hope its worthy of discussion. I just bought my first jeep about a month ago. Its a 1999 tj 4.0 sport. The po was the original owner, it has 132k miles on it, superlift 4" suspension lift, 35" buckshot maxxis tires, hardtop, good looking rig. Anyway, he had replaced the faulty header with a better one supposedly and put a flowmaster muffler under it (kinda raspy sounding) but cut the catalytic converter out. He said he did it for performance, but I think he did it because cats are expensive and he didn't want to pony up the dough for a new one. So I have the wires for the rear O2 sensor taped up and tied off. I have put about 1000 miles on it since I have gotten it (who knows how many he put on it like this) and it seems to run just fine. There is no gassy smell, no sooty exhaust, I'm not overly concerned. The only thing that bothers me is that rear O2 sensor not being in there, I know the computer gets a reading and adjusts the fuel mixture based on the difference between the first sensor and the second one, but what is that missing sensor telling the computer? Guess I could pull a plug and see if its rich or lean? I am considering welding in a bung and replacing the sensor. Im not overly concerned with the missing cat, I don't drive it on the road THAT much, just buzzing around the farm (literally, the thing sounds like a bee with that flowmaster and no cat). Thoughts, experience with this?