Like Dennis said, The OXS sensor might be a place to start. Let's look
at your numbers.

HC was at the limit at 2600rpms, and above the limit at idle. That
means you aren't completely combusting your fuel. Under normal
circumstances, the catalytic convertor will help reduce HC assuming you
have enough Oxygen in the emissions for the cat to burn the HC....

The CO readings confirm this. The limit for CO is 1.20, but you're up
in the 8's at both rpm speeds. That means you have too little Oxygen in
the exhaust so that you are forming CO instead of CO2.

Probably also worthwhile making sure that your air filter is clean.