I removed the EGR and jumpered the terminals between 12v and ground. All the solenoids/pintles open. I confirmed that the EGR valve passages are clear with compressed air with the pintles opened.
I left the jumpers in place and re-installed the EGR. With the engine running at idle I connected the jumpers between 12v and ground. The engine would stumble and want to stall when the EGR terminals were grounded (one by one). So the EGR passages are clear.
Signs are pointing to a bad converter.
What's bothersome is that the O2 sensor is reading a rich mixture. I'd like to correct this before installing a new converter. I need to go back to my notes and confirm fuel pressures, etc. and re-read the FSM for specs that are unclear.
Thanks for all the help that's been provided.
Just a data point; I replaced the plugs (when I replaced the O2 sensor) and they appear as they always have in the past.
Plugs - 27,393 miles; in order - 1 thru 6 (5/22/16)
Typical plug (42,369 miles) with new replacement (8/20/11)
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