I found what the problem was a few days ago!!! I am posting this because I know that there is somebody out there looking for an answer to this just like I was. Just to give a few essential details again I will mention that I have a 1995 XJ ( I know...its NOT a wrangler but w/e its the same drivetrain) with a 2.5L and an AX-15 manual trans (swapped from AX-5).
I have replaced almost all of the sensors in the last 3.5 years since I rebuilt the engine because either they failed or I thought they failed. I checked everything and I mean EVERYTHING I could think of and ended up just swapping a few parts between my two Jeeps (other is a 1995 with 4.0L and AX-15 trans) until I found it. It ended up being a brand new MAP sensor that I had put on there while trying to find a solution to what was at the time a much more complex set of symptoms because of multiple simultaneous problems. I bought a new MAP sensor once I found it was bad and it has run great!
Just so you know here are the symptoms I was getting: Would not rev past 4000 RPM no matter what I did and acted like it was bouncing off of the rev limiter right when it would hit 4000 RPM, some hesitation esp at low RPM and a noticeable loss in power all around (not a lot but def perceptible), occasional backfire up through the intake esp at low RPM when using a lot of pedal, running rich. It was not running rich to the point of smoking but if you went to the tail pipe it would make your eyes water/burn and your nose would burn too from the fumes of unburned fuel. I never got a check engine light/code on the 2.5L. I even did the key trick (on/off/on/off/on and wait for blinks). However I DID get a check engine on my 4.0L engine when I put the bad MAP sensor on it! In fact the 4.0L engine would not hardly run with the bad MAP sensor installed! That is strange to me because they're the same thing other than 2.5 vs 4.0L....meh whatever.
I really hope this helps somebody someday as I was looking everywhere and found several threads but NOBODY would freak'n come back and post what they found, so here you go, my golden nugget to you