Hi Mike
I hope what u say is true, because mines failed miserably too.
My 90 300 se does have an airpump, to wire her on while going thru smog test is no big deal. It will cost me $23 to test, but is worth to validate your hypothesis. The extra air will burn off the extra hydro-carbon, reduce the CO.

I have already unplugged the air valve, it did improved the idle test.
Before anything was done, the car failed in just about all count. And the exhaust really stinks with too rich gas. Some guy offer me a used working O2 sensor for $40. I haven't had time to pursue it yet.
I live in Vancouver BC we have www.aircare.ca the good news is they will rendered emission test to become History in 3-4 yrs, as newer cars are so clean, so we'll be receiving our Get out of Jail free card soon, but not soon enuf. i wanna my cake & eat it NOW.
I hope I can give u good news very soon.
I have tried stud tires as a chap told me, with stud tires it wont be allowed on the dyno drum. But no serie Bob they did the test as if nothing had happened, or the poor testing employee had been rendered redundant already.
I do start to feel like I am WIley Coyote or Wicked weasel always try to beat the system at every instance.
pray I get thru. God help all of us.

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