Well, if the Jeep's always had high octane fuel that's not the culprit.I run the highest available octane. In my area that is 93. Out on the trails it is typically 91.
Good call on the air cleaner. I've likely done 1000 miles off road over the last year or so which includes water/mud up north and desert out west.
I'll likely replace - what's the best replacement filter? I'm not looking for a CAI for 'whooshing' noises - I need to keep it protected from the elements.
I've had good luck with K&N air filters for trail rigs that see a lot of dust. There are a lot of people that don't like them though. I think a CAI is a waste in this case. You just pick up a couple of ft-lbs in the upper RPM range and often lose a few down low where we're talking. I would just get a quality replacement filter like AC or Fram or whatever.