Just in the interest of helping anybody who has this same problem,
here's the GM fix so far. I took it to big GM dealer early yesterday
a.m.. Sat and waited for emissions guy to get in. He took one look at
previous test results and said, "Oh, you're running 89 octane, aren't
you? (yes, I was) "Run it out, run a full tank of Chevron 93 through
it, bring it back to me when its almost empty. I will test it while you
wait and I guarantee it will pass."
He never even looked at the truck or tested it. He told me, "I don't
have to look at it. There's nothing wrong with your truck." He
explained that -- since '99 and later 2.2 do NOT have an EGR system --
many are doomed to fail new, stricter CA NOx standards at slow speed IF
you take the test on regular (89 octane) gas.
Well, so at least the EGR controversy is settled. It'll take a while
to run a full tank of 93 octane through it. Then I'll take the test