get a dynomax mandrel bent tailpipe. I had a header high flow cat and a super 40 with a stock tailpipe and going to the mandrel bent woke up the exhaust note big time even my old man commented on how good it sounded. we got deal on the dynomax super turbo and tailpipe for his xj and it has a nice mellow sound to it without the volume of the flowmaster. I just put some thrush welded (flowmaster knock offs) on my truck and have been really impressed with the sound for half the cost of a flowmaster. If I was gonna do another exhaust on a 4.0 jeep id probably go with the thrush welded muffler and the dynomax mandrel bent tailpipe.