Sorry for the book in advance.

Alright, so here's a little backstory:
1994 EJ1, had it for 10 years, on my fourth engine swap, went through an unlucky streak over the last few years with blowing up engines. I had the stock D16Z6 that hydro locked and spun a bearing, swapped that for a 1991 B18A1 that (a few years later) had the oil pump fail and spun a bearing, swapped that for a 1993 B18A1 that also probably spun a bearing (again, a few years later).

I blew up the 1993 B18A1 last week, I am now sitting on a 1996 B18B1 that I installed over the course of the last week. Thing is, I've never had so many issues with a B series firing up until now. This thing DOES NOT want to run. Before anyone says it, yes I've swapped out every single OBD2 part for the OBD1 parts that were running my previous engine (intake, wiring harness, distributor, ECU, etc.) Effectively I have OBD2 to OBD1 swapped the engine because I lack the funds to simply run OBD2 (ie jumper harness/new ECU, etc).

Now, I've gotten it to fire up and idle. It works, the engine does its job. However. It's... Dieseling..? On the 5 or so times I've gotten it to run, 3 attempts were met with a horrible screeching noise (like there's rocks in the engine trying to escape) accompanied with smoke billowing out of the intake filter (smells metallic, like clutch, but different?). I've never seen or heard anything like it before. It's honestly gut wrenching to listen to (and smell).

Attempts went as follows:
1st start, 1 sparkplug wire disconnected to figure out if spark was an issue, sputtered to life on 3 cylinders before promptly dying.
2nd "start", horrendous screeching sound, smoke rose from the engine bay, mostly from my intake, sharp metallic sound and smell, and it died. Like it was running away/dieseling.
3rd start, today I had it start, sounded PRIMO, no issues, perfect sounding internals (I was spooked about the noise it made on the 2nd start fiasco), no lifter tick, knock, nothing. Purely perfection. Turn car off to button things up.
4th "start", noise came back, this time with the the same issue, smoking out the intake manifold, horrible screeching noise like it was high idling and running away with it. Smoke smells metallic and almost chemically.
5th "start", same as the 4th try, but this time the duration of it staying "on" was shorter, but still horrible banshee like screeching from inside the engine and smoke.

My question is, what is causing this? Obviously the easy answer is "just get the jumper harness and run all the OBD2 stuff" but the thing is, I shouldn't -have- to do that, seeing as it fired up all four cylinders and stayed running until the key was turned off without any problems on the 3rd attempt, I have it all wired right, all the plugs are in the correct spots, all the hoses are in the right places. We're getting fuel, air, compression, and spark. What the hell am I missing here? It's been driving me insane, and nobody on any forum post has ever come forward with the same issue. Please, please, please help me figure out what this issue is 😭

Picture attached is my swap before I figured out where the circled water nipple went (B18B1 goes to front passenger side of the engine with this, B18A1 goes to thermostat housing, had me stressed for a bit). Also note, everything in this is B18B1 parts, I had a B1 intake manifold on my A1, running a P75 ECU meant for a B1, distributor for B1, etc. I had the ECU essentially fooled into thinking it was running a B1. Remember, it's started on all cylinders without issues on attempt 3, which rules out most everything I can think of.

(Pardon my filter, smoke season has not been kind to me)