From what I can see there are 3 cats on my 04 TJ. Two before the Y juction and one after. I noticed that there is one O2 sensor before and after each cat that is before the Y junction but there is no O2 sensor for the third cat. My question is..Can I remove that 3rd. cat and not run into any problems? I just stuck a flowmaster under it this eve. and noticed that cats. The muffler sounds great too. Whoever had the flowmaster before me had blown their engine and shot a bunch of oil through it so it smoked like a chimney when I first fired it up. It was kinda funny watching the subdivision fill with smoke..lol Anyways any help in this area would be great.