Hi there here is the Lambda to AFR conversion table
Knock can be engine noise,gearbox or something touching the manifold etc.Without the det cans you never know for sure what can be or cannot be.
Just check the logs and have look for ignition retard and how much ignition retard pull Syvecs when you are get knock,second thing when you are get knock,have look when this happen if is under load or gear shifting etc
Jura