1998 Jeep 4.0 ltr H.E.L.P

Howdy fellow jeepers,
SO I'm re opening a discussion because I can't find someone who has the exact same issue as me. I've looked everywhere.
All that aside, i orginially had an exhaust header leak, and I let it go too long of course, and so finally it got to where it sounded like my jeep was falling apart.
So I replaced the header, and got it all back together, cranked it and it backfired into the manifold. So I blew a valve seal. That eventually turned into me overhauling the whole top end. Brand new head, seals, valves, rocker arms, rods and all new gaskets etc. So after I put the mothership back together, I cranked it and it ran super rough. And it has ever since. It stumbles at idle and stumbles and misses through 1800 rpm. But at 2000 it smoothes out and drives fine but as soon as I let off the throttle, it goes back to its bad habit. And it's constant every time. I've read that some people have this problem only ever so often. And I've checked for vaccum leaks. Checked injectors, fuel pump is fine, throttle body is fine. The only things I haven't checked is the IAC and TPS. I ordered a new CPS a couple days ago, because I knew it was bad and I've heard that that sensor could be my problem, but the one thing that I've concluded is that my valves aren't "set correctly". I was told that I was supposed to bring every piston to top dead center and make sure the rocker arm is loose in order for all the valves to be set correctly. I know this is super long and a tad bit vague, but can anyone help me? MANY THANKS.

Checked for codes and checked map sensor?

The codes it's throwing are pointless, I've checked em multiple times.

I see you have duplicate threads. Can you kill the other one?

Here is my response on the other:
Non champion plugs? Mine and other's have done the same thing with other brands that have the same specs and should work but don't. I think it's just like using a Bosch O2 sensor, though mine actually seems happy with that one while lots of others aren't.

Yeah ill delete the other one, my bad.
But on the plug issue, im not sure what brand plugs they are, i believe they are NGK but ill have to check. They are brand new though, along with the wires. i dont have an exhuast O2 sensor, as i dont have the cat. But that code has been cleared( i have my own DB2) but anyway, the only things i havent done is change the map sensor, and i dont have the new CPS yet. Hence why i am stuck. i dont believe its the IAC due to the fact it smooths out at 2k.

Not having functional O2 sensors will cause the symptoms described.

By the numbers, what are/were the Trouble Codes present ?

You can't fix something if you don't know what is, and what is not, causing problem. What systems and OBD-II sensors have you tested and found to be operating within specifications ?

NGK's are my goto plug and when I put them in, I had this same issue.

okay so first, the code numbers thrown were like 8000 numbers and I looked them up and they werent anthing that had to do with air, or fuel system etc. I dont remember the exact numbers but i can read them again if it really could be something that simple. But the reason i dont think it is this O2 sensor is due to the fact that before the Overhaul happened, it ran completely normal.

Did you pull the distributor when you did the work?

You have no downstream o2 or both? I had a 98 once doing about the same thing. Unplugged upstream o2 and would run much better.