Scratching me head...new BMW owner.

[Kershaw]

I'd also swap your tuned DME with a stock one and see how that changes things.

[Ether-D]

The continuity test can be a false negative. If the wire is not warm enough to be touching the pulley it will test good when it's bad. I think they are about $40 on eBay.

[Jdbush2010]

That was going to be my next thing to check. I'll honestly be super upset if it is cause I looked at that thing and thought about it and never checked. I'll consult my Bentley manual and test it accordingly

[Ether-D]

Crank sensor would be a good one to check. The wire gets chewed by the crank pulley and it can ground out erratically causing your symptoms.

[Jdbush2010]

So I just recently bought my 1986 325es. I've been searching and searching and trying stuff but to no avail. Specs on the car:
1988 super Eta 2.7it bottom end
1988 2.5it head
Full motronic 1.3 harness
Intake swap
272 cam
E36 Bosch blue top injectors
Tuned ECU by MarkD
Ireland engineering long tube headers with MagnaFlow muffler

Here's the problem I'm having. It runs super rich after a few minutes and hardly wants to idle. Sometimes it's great for a little while longer depending on how hard I beat on it. When driving at minimal throttle cruising it will start to buck and miss and sputter but when I give it more skinny pedal it clears out and takes off like crazy. I don't like running it that hard must to be able to drive. It's my daily so I have no other options but to drive it.
If it acts up and I beat on it it will clear up and be fine for a short while then start again.
I have checked for vacuum leaks, no smoke test. Just the carb and coke cleaner method.
Changed both coolant sensors (gauge want working properly)
Changed maf with known working unit as well as tps, icv, icm, and fpr.
Put new plus in, and it helped some
Checked the o2 sensor and it was dirty, I was assuming it was due to running rich. The hard wires were also twisted and black taped... So I stripped them back to the good, non corroded parts and soldered and heat shrank them.
I did check the c191 and went ahead and did the fix for that for good measure.
Now I have gotten the car to run great with no problems for a couple days last week... Then it returned just as I was telling my buddy how glad I was that it was fixed. Just my luck.
So here I am not knowing what it is or how to start.
I have only tested one thing and that was the cts. Coolant sensor tested good. Had the correct resistance. Now when I checked the ecu it wasn't cooperating. Cts read I think 330 ohms whereas ecu was reading somewhere like 1400 ohms if I remember right.
Any input is nice. Sorry if it's in the wrong section, this is my first post and I'd really like to enjoy my car. I was pro gm before but love my e30. Thanks! I hope that's enough info