1992 Jeep Cherokee Sport. Jumping, stalling when it heats up.

I have a 1992 jeep Cherokee sport that is giving me quite a headache & it seems to be getting worse. My jeep has 272,000 miles on it. Bought it used almost 5 yrs ago. Anyways, starting back in april when it started to get warm here in Pennsylvania, it started to do this thing where you'd be driving it at 45mph, the tac meter (thing that reads RPM) starting to bounce up n' down from 800rpm to roughly 1500rpm. It would bounce like that for every 2 secs while driving. Now, when i went to slow down to roughly 35mph & slower then that, it would begin to spit, sputter, jerk, & carry on & it shut off on me once!
It seemed like it got a mind of it's own too. When I come to a stop, it seems like it wants to give it more gas!!! There are acouple of times that I almost didn't get stopped & almost rear ended acouple of cars!!
When you go to park it & let it run, it sounds like someone is pushing down on the gas & letting off of it every 3 secs. Again, it would go from 0rpm to 1200rpm then keep doing that til you shut it off.
If you shut it off & leave it set for about an hr then, it'll run just fine for about an hr or so & then, begin to mess up!!

So far, I've changed, the plugs, plug wires, dist cap/rotor, 02 sensor, swapped a MAP sensor off of my moms jeep, (no change there) The last thing I just bought was a Ignition coil. Mine had cracks in it so, I thought it might of been that. NOPE!!! Still messes up. It seems like the hotter it gets outside, the quicker it wants to mess up. I've even got a can of carb cleaner & sprayed every vac line/hose that I can find. No change!!

I DO NOT KNOW WHAT ELSE TO DO!!!!!:banghead:

Can anyone give me any ideas?

Oh. One more thing. On cold/cool mornings, it'll start up & run just fine even with the bad coil that was on there.. No problems.

well, after spending most of the day online researching, I found a way to get the codes off of my jeep by using the key test & counting how many times the check engine light flashes. I did this today & from what I gather, It's giving me a code 23. (incoming air temp sensor may be going bad) which some people call it a Manifold Air Temperature sensor. (MAT)

Could this really be the problem? I didn't get any other codes except a 12 at the begining a flash, pause, flash, flash.

Then, flash, flash, flash, flash, flash, pause, flash, flash, flash, flash, flash. Code 55 to say it was done.

Throttle position sensor?