The fact is you'll get lot's of different answers from lots of different people about this. If the tuner has done a good job there should be no pinging, check what the highest level you get under hard driving conditions, add a bit of a buffer, and you will have a reasonably safe knock level. If 23 is the highest you've achieved while driving hard, then it shouldn't go much past 30 unless something has changed, so might be worth backing off to check.
The knock sensor picks up all engine noises, not just pinging, so the level will be different between cars.