Ok I was pulling into Auto-zone tonight, I let off the fuel and half way through the 90degree turn the jeep shut down, shifted into Neutral hit the key, and it came back on. I put a cat back exhaust on it in April, because it was idling low, about 350 to 400 RPMs, and all engine sensors MAP, MAT, TPS, etc checked out the only one I was unable to test was o2. The cat is universal (I have used this one in the past on the 4.0) Cherry bomb muffler (the traditional pipe style) and new tail pipe. For about the last week there has been what sounds like a heat shield rattle when shifting from forward to reverse and vise verse, the Jeeps body has 268,000 on it so a rattle was no big deal. It has been off road with the new exhaust or through any water. Is it common for a cat to come out of factory messed up. Please help I am in college and need this for commuting, and I don't have the money to throw at problems like I used to. Thank you for taking the time to read this, and for any advise you can give.

P.S The Engine Transmission and T-Case only have about 75,000-80,000 on them.