2.4L Engine Problem
 

When I had about 20,000 miles on my Jeep, it developed a bad stalling/loss of power, not just at idle but also randomly while driving. It wound up getting so bad that it just had zero power all the time and I finally got my dealership to take a look at it. It wound up being that the Cat was clogged. As soon as they replaced it, the problem went away for about 5,000 miles then it kinda started again but I got a check engine light this time. This time I had a bad spark plug, I replaced all the plugs and wires and it ran better then it ever did. Now i have around 47,000 miles and this whole thing is starting again, but this time there is no check engine light and what sounds like plenty of backpressure in the exhaust so I don't think it's the cat. Are my plugs just bad again, even though I put Iridium plugs in last time? I also just realized today that besides at idle, the problem is generally under medium to heavy acceleration between 2,000 and 3,000 RPM's. Outside of those conditions it drives fairly smoothly.