SUCCESS!

Switched #4 with #2 and the problem moved to #2. I did every possible test on the bad injector when I had it out of the engine. It ohm'd out OK at 14.6 with the spec's saying 13 to 16. I was able to open the valve again with a 9v battery. I did a continuity test on the wires and used a noid light the verify ECU firing.

This has been the most frustrating problem I have ever had. I can only say that a running voltage of 12 - 13.6 somehow caused the injector to not fire. How is that possible unless there was extra heat in the coil at that voltage that shorted it. Comments welcome.

So taking the plenum off again (I think this is #4 since last summer), but at least this time I have confidence that I can solve this problem by installing a new injector.