Strange Idle Issue - Input Appreciated

I have read almost every single other idle thread out there and found a few similar issues, but the solutions did not seem to work for me. So when I come to a stop, my 99 XJ's idle will not settle. The tach needle bounces up and down (not by much, but its constantly bouncing). It seems like it does it worse when it's cold, but it does it when warm as well. When I come to a stop at a light, sometimes I can feel the entire Jeep shake. It runs good for a few seconds, then shakes for a few seconds, then runs good, and so on. So far, I have cleaned the entire throttle body, cleaned and replaced the IAC and TPS, ran seafoam directly through the throttle body, ran Lucas injector cleaner through the tank, replaced the spark plugs, wires, cap and rotor, and replaced the ignition coil, all to no avail. I tired disconnecting the upstream o2 sensor and running it, but that didn't seem to do much either. I'm thinking it is either an o2 sensor or a bad cat. When I'm driving down the road at any speed above 25 mph, letting my foot off the gas and just coasting results in the idle bouncing around (it comes down, jumps back up, comes down, etc.). Any input would be greatly appreciated. Thank you.

is it possible that you've got an intake leak that the IAC is trying to compensate for? The IAC isn't very quick so it tends to open and close slower than it should for large vacuum leaks.

What did you replace the TPS with? This is one of the few items on our beasts which is best renewed with 'genuine' parts. I had it go on my '96, with pretty much the same symptoms you've listed. Some 'name brand' items didn't help. So I went to the yard and grabbed a few, found one that it was happy with, and for over two years now, it's been fine.

I actually replaced the TPS with another (used) OEM one that I had sitting on an extra throttle body. I was planning on just testing it this way and then if I determined that to be the problem, I was going to go purchase a brand new one. However, it didn't seem to make a difference. I checked for vac leaks as well as intake leaks. I don't think I have any. I'm considering ordering a set of new Bosch 4 hole injectors.