Here are, in generic terms, some items that can cause elevated CO readings:

1. dirty or restricted airfilter
2. contaminated oil
3. saturated charcoal canister
4. non-functioning PCV system
5. dripping fuel injector (s).

I am still puzzled, how you can have a high lambda reading ( indicating a lean fuel mixture ), and yet have high CO's.

When was the last time this exhaust gas analyzer was calibrated ?

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2007 C 230 Sport.