There is something wrong with this picture. I have been doing smogs for 20 years so i have some clue on cars. Anyway the nox repair went very well. Looks like you did the correct repair the first time. You would be supprised how often people fix every thing but the right thing.
So you had great co the first time and now car is not in fuel control. should have about .15 co give or take a little.
So first check to make sure no wires were left off during the repair, most likley cause.Also check for air leak after the m.a.f sensor.
Co can go nuts like this if coolant temp sensor is disconnect or out of range. Shold throw a code if its that bad.
Second your intake air temp sensor,is it disconnnected? If its on , if its hooked up move to the 02 sensor. Hooked up? Maybe its drifting or out of range. Some times no codes and most likely cause of co problem.
One more important item i almost forgot, you moved the wire harness around alot during the repair,this could make all those sensors act up. Double check to see if the wires are not falling apart, this should be the first thing done.
fixing nox is no reason for co to go crazy.
Good luck
Rich

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88 300E White, sold 9-04
88 190E Black 2.3 sold
90 300CE White, Grey sold 12-24-04
92 400E White,Grey Sold 5-06
90 300CE 91K Signal Red,Black Sold 2007
1989 300CE Smoke silver,Tan Sold 1-08
1993 300E 3.2 M104 motor
1991 300CE White,Grey
1994 E420 beautiful car,gone to new home
1994 E320 Smoke an Parchment.Beautiful car