new to me 1991 e30 with m50 swap I need some advice/help (engine running rough)

[skater4145]

ok guys/gals,

I need some help... i was able to purchase/save an e30 chassis that is m50 swapped... and surprise, it doesn't run very well. at idle its lopey and sounds like a racecar, give it a little gas and it hangs at 3k rpm for a couple seconds then comes right back down to 900-1000 rpm.
So I look around the engine bay... ohhhh boyyy y'all are in for a treat. so lets dig into what ive found and done so far.

INFO SECTION:

found:
1. no maf or o2 sensor
2. no smog equipment
3. aftermarket chip in dme
4. porsche (944?) brake booster
5. aftermarket header
6. wiring is snafu
7. pulled spark plugs and they are very dark (im not surprised)

done:
1. tested cylinder compression
cyl 1: 179psi
cyl 2: 180psi
cyl 3: 180psi
cyl 4: 175psi
cyl 5: 175psi
cyl 6: 170psi

2. tested ignition coils/coil wiring/spark plugs
all 3 components tested fine. tested with a cheap amazon kit with the light bulbs and everything checked out ok.

thats it so far. my next move is to make my own diy smoke machine and test for vac leaks. after that i will check fuel pressure.

but i need some guidance from bmw owners here.

so previous owner said the car was running pretty well, then started acting up like it is now out of nowhere... he is my co worker and he showed it to me before it started acting up and i can verify it was running and idling "ok"

QUESTIONS:

A. how on earth does an m50 run even halfway decent without a maf or o2 sensor?
i know it can be in open loop but I thought an ecu needs at least some feedback on incoming air mass/volume?

B. what will happen if i start hooking those items up?
ie. maf and o2 sensor and emissions controls

C. what should i start hooking up first?
(assuming vac leaks and fuel pressure is good)

thank you all and here's some pics so you can see what im working with...

[e30strokr]

I would start with adding the OEM chip+ MAF and O2 sensor..... and check for leaks.. I didnt know you can use the M20 intake tube.. are both holes plugged?!?!? also that line going to the throttle on the bottom seems collapsed

[Northern]

Probably has some sort of alpha-n chip (throttle angle vs RPM) but you never know lol.
I don't know how that ECU deals with that, the tables that they usually use are just for limp mode stock so they're probably pretty small/crap resolution.

I'd try to find a stock chip (or just a whole other red label 413) for hooking up the MAF & O2 sensor.

That kinked hose looks like it's on the throttle body heater lines, and can probably be removed.