Thanks for the quick reply, Duke - this is great info. First, to answer your questions:

1) 137k, tested this morning.
2) Far as I know - and I have pretty complete history - the O2 sensor has never been replaced.
3) Software version 310/WP391284.

Temps were pretty warm this morning, better than 85F at time of testing. Drive over was about 15 min, and about a 20 min rest before testing - which went by pretty quickly. The EGR test 'result' is N/A, but far as I can tell there IS a valve. It is bolted to the exhaust manifold, and has a metal pipe leading around to the intake, and a vacuum connection to something.

I was wondering what the high O2 reading at 15 mph signified, so it's nice to know what the mechanism is now. I'll be digging into more of your posts on this. Thanks again!

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7