I cannot think why a Lambda Sensor will switch that slowly unless it is faulty or clogged by carbon.

Pinking can be caused by various problems such as incorrect plugs, carbon build-up, weak mixture etc. However, I would have thought the knock sensor if working correctly would deal with a certain amount of pinking. Nonetheless, that would not explain the slow switching of the Lambda sensor. The sensor needs testing irrespective of its age.

Regards

Pete M