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<e28> Motrinic Problem - Dead 528e

My '84 528e mysteriously cut out on me a couple of weeks ago.  I was
driving along, and suddenly, the tach drops to 0.  Afterwards, I was
able to start it a couple of times, but it would just die after less
than a minute.  Out of the past 12 yrs of owning BMW's I've never
gotten stranded; I was flabbergasted that I'd have to get towed for
the first time.  Things are not so simple on this car like my
carbureted 2002.

I first tried swapping DME and ICM from my 325e (both of which I know
have worked before on my 538e).  No luck.  Next,
I went thru the whole procedure in the Bentley book, checking all of
the inputs to the DME.  Everything checked out ok, so I plugged the
DME back in, and the car started!  Ok, so maybe it was just a bad
connection?  I drove it a couple of days, and then boom, it dies on me
again!  

I rechecked all of the DME inputs.  All ok.  Good spark.  Fuel pumps
are running.  What the heck is wrong?
This time, I'm fed up after re-testing and finding nothing wrong, so I
get it towed to this shop a couple of blocks from where it died.  So
they call me up and tell me a need a new DME box!  Such an easy
cop-out.  I pulled the box from my 325e and took it to their shop and
plugged it in.  Still didn't run.  Of course not.

So he shows me w/ his test light.  Sometimes the injectors are getting
a signal, sometimes they are dead.  At least I convinced him that the
"computer" is not the problem.  So he says "At first, small job, big
money, now is big job, small money.  Today busy, how about I check
tomorrow?" 

That was Saturday.  He still hasn't figured it out.  Does anyone know
what things I haven't thought of that might cause the injectors to not
get any signal?

Questions:
1) AFM.  Is the resistance supposed to change smoothly when you open
and close the flap?  Mine seems to jump around.  I've checked/cleaned
the wiper and it looks fine.
2) Can the reference or crank sensor be the culprit?  in light of the
fact that the spark is consistent, i'm skeptical of this one.  bentley
only gives a static resistance value.  i tried measuring voltage while
cranking and found that it went up while cranking.

Any help would be greatly appreciated.

Sam