I'm once again struggling throught CA emissions tests and would like to share my test results with participants in this thread:

First Emissions Test since passing in 2007

MPH=15 RPM=1507 %CO2=14.9 %O2=0.2 HC(PPM)=84 CO(%)=.30 NOx(PPM) =1032 FAIL
MPH=25 RPM=1530 %CO2=14.9 %O2=0.1 HC(PPM)=43 CO(%)=.24 NOx(PPM)=525 Pass

Replaced CAT with an aftermarket model (Magnaflow).

MPH=15 RPM=1498 %CO2=11.6 %O2=4.6 HC(PPM)=28 CO(%)=.09 NOx(PPM) =944 FAIL
MPH=25 RPM=1488 %CO2=11.5 %O2=4.6 HC(PPM)=21 CO(%)=.08 NOx(PPM)=899 FAIL

Reset duty cycle (enriched mixture)

MPH=15 RPM=1520 %CO2=15.0 %O2=0.1 HC(PPM)=53 CO(%)=.03 NOx(PPM) =1508 FAIL
MPH=25 RPM=1793 %CO2=15.1 %O2=0.0 HC(PPM)=44 CO(%)=.06 NOx(PPM)=1156 FAIL

Why did CO drop so low after replacing CAT, and stay low after enriching the mixture? I would also have thought that NOx would have decreased after eliminating O2.

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Steven
1989 260E (276K miles)
1995 E320 (50K miles)