Steve aka gunner, No KR is good KR or acceptable KR. KR means your motor is seeing predetonation and it'* reacting after the fact.
Predetonation cracks piston skirts frequently in our motors, leaving the top ring exposed as well as sharp edges. Sharp edges heat up more and cause further KR. It'* a brutal thing that you want no part of.
A custom tune..totally necessary, not at all. Scanning, well that is pretty necessary. If you tuned and knew you were good for no KR, then you wouldn't need to scan until the weather changes. Then the tune isn't right again.
Mid level has a tune
Good has a tuner