OK,
Replaced the wiring harness, the old one wasn't all that bad off, but when I bought the car I was warned that the time was ripe (14 years) to replace it.
Checked the fuel pump pressure, just fine (~50 psi). Checked the intake manifold vacuum. seemed good (~15 Hg in, no wobbling), didn't spot any leaks, though the engine runs pretty much the same even when I've disconnected a hose.
I ran through the other diagnostics (thanks to the tested I built thanks to Dean's schematic). On pin 6 I got code 13, stop lamp. On pin 7 I got codes 5, 6 and 11. The only one that seems relevant is code 11 which says "Fuel safety shut-off to LH-SFI control module". Pin 19 yields code 19, back to "Injector open or short circuit or emission control adaptation at limit". Code 20 has not (as yet) returned. Pin 30 yielded codes 3 and 8, which I don't think are relevant to the problem at hand.
G. Johnson has suggested the air mass sensor, though I would hate to replace such an expensive item without further testing. Does anyone have any suggestions on what I could look at next?

JimF, what would cause the emission control system adaptation to go beyond the limit? I would rather get it back in limit (if that's reasonable) than to change that chip to accept a wider range (which is what I understand it would do).

Oh, I assume I'm doing no damage driving the car.

Many, many thanks. -- Greg

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Greg Stein
'94 E420
'86 420 SEL
'79 300 TD