You cannot adjust FI for CO accurately without a CO analyzer. Two things to consider. VW sets CO via the test port AHEAD of the cat. This gets the engine right and then the cat takes care of the rest for the EPA'ers. 2nd, if you have high idle, it usually indicates a sensor is out of specs. For the most part, those can be tested per the troubleshooting chart. Temp sensors can be tested out of vehicle with a pot of heating water. The Bentley is the factory manual so assumes you have a basic understanding of auto ops & repairs. But it is far better than the aftermarket junk, which often contain a lot of errors.