This has been going on for a while now I just haven’t had the time investigate it. On start up the jeep makes a bit of a ticking noise but goes away once it is heated up. Doesn’t happen every time but it is frequent. It is a 1998 4.0 3spd sitting at around 130k miles and a seemingly stock manifold. I have read that the early model exhausts were too rigid making me suspect it is a manifold crack. Gas mileage has also been a bit low recently but I have only been doing city driving 20-40mph and getting 11-12mpg.