I am looking at KR1, KR2, KR3 on the AF gauge & it seems only KR1 gives me a reading which now makes sense based on the explanations above. A few of my mechanic friends suggest that if detonation was in fact occurring, I should be able to hear it but I am not sure what to expect with a GP? I could hear detonation on the SN95 5.0's no problem.