....and the problem was.....
Brought my E150 to an emissions shop who did a vacuum system 'smoke test'. Sure enough, the EGR was emitting smoke badly.....so the suspected problem was an EGR vacuum leak. However, it was suggested I replace the fuel filter. Sure enough it was really cloggged. Replaced it. Replaced the EGR myself...a real pain to do. 'Codes' gone. So, it appears either the EGR alone or the fuel filter alone, or some combination of the two, was the cause.
FYI