M50TU code 1283?

[gt90]

I figured I would post this here seeing as all the other bmw forums aren't nearly as helpful, and this engine is also in 525's right?
I have an M50tu in a 1993 325is that runs great for about a minute at start-up idles around 800-900 and then starts to sputter a little bit and eventually goes into a "lumpy" idle around 600-650 that makes the whole car shake. The bentley manual says the code is "fuel injector output stage".
I already replaced an injector that was causing a CEL, and I cleaned the ICV.
Also removed the coil packs and spark plugs and cleaned the oil out of the wells (don't think this was the problem though as both top and bottoms of all spark plugs were dry). I have no idea how old the coil packs are but other than some white coating on the springs in the boots they look fine.
Also when I unplug the airflow sensor the idle jumps back up near 800 and is perfectly smooth for about a minute, basically it just repeats what it does at start-up. Could this be a bad MAF?
And when I drive the car it hesitates and has a loss of power until around 3000rpm's. Any insight as to what could cause the loss of power and the 1283 code?
What should I check?
Thanks for any help and sorry for the long winded post.

[BillionPa]

there is a timer in the ECU that advances ignition timing and injector pulse width "post-start" for usually around 30s (could be a minute in the M50tu). One of the signals the ECU sends out goes to the idle stabilizer valve. During warm up, to increase rpms it opens the valve more.

I would use throttle body cleaner and MAF cleaner, and clean the hell out of both.

I would also use a fuel pressure monitor to see what the hell is going on when it starts to sputter. A failing fuel pump or clogged filters could mess things up.

If you dont remember changing your fuel filters in the past year, do it now!

If none of those work, the ECU itself (which controls the injector pulses) could be screwed up or have a bad map somewhere.

[gt90]

Thanks BillionPa I'll try that today.
Anything else I should try, this hesitation and lumpy engine is driving me CRAZY!