I have a stock Knock sensor.

Car would sometimes do it before the tune.
Put in bigger valves when timing jumped and motor mounts now its flashes at any amount of throttle even just trying to get to the posted speed limit at talking less than 10 psi/ Car is only on 18 psi right now and still will do it under full boost from time to time.

Would a small scratch on a piston make this happen?

 

No, a small scratch would not do that. It is best of course the crown of the piston to be without imperfections. It matters not if you are on 10 psi or 100psi, if the tune is wrong, and I am mostly referring to the timing table in your case, could actually cause real knock.





Marios

 

I guess i would call it a little knick. that has been polished down a little