For anybody trying to fix their AFM..

Just had my AFM tripping the ECU and the car wouldn't start.. checked against BGB values and literally everything was out of spec (one of the readings was reading 0 ohms which is the one that was tripping the ecu)... 40 mins later with a load of contact cleaner and a soldering iron and I'm back in the game running again (fingers crossed it keeps that way...).
 
First, take it out of the car and open it up, I just used a flathead screwdriver and went around the edges trying to be careful, used two screwdrivers in the end to jimmy it, here's a video I took because seemingly nobody's ever made one of the insides:
https://www.youtube.com/watch?v=-jYP3Ug3BaM
 
Second: So basically, the AFM takes 3 measurements: temperature, the actual airflow potentiometer, and a third that I'm not 100% sure on but I think it might try to estimate the gas constant or something in order to do PV = mRT calculations to figure out the pressure or volumetric flowrate. 
 
Third: So my readings were ALL out of spec, basically the wires attaching the contacts to the PCB were gone... bad solder joints (from the factory? or maybe just the tale of 25 years) and dirty connectors. 
Clean up everything, fix up the connectors, and then use your multimeter to check the resistance on the output terminals and make sure they're all in spec according to the BGB (mine were again). 
 
Chuck it back in your car and enjoy.

The only reason I didn't post that was because I figured everybody knew about that adjustment already haha
So was yours actually not in spec without having been dug out?

Interesting - I had always assumed that to even get to that screw it had to be drilled out therefore access to it almost implies its been moved, good to note.

I'm also somewhat surprised by black smoke... Most people I've seen with dodgy maps of afms in the past will get white smoke. Wonder what the afr was reading before... Doesn't sound like the o2 sensor would have been having a great time