[Maylands Performance]

Hi Pitmaster.
The piston shows some scuffing at the top of the piston above the ring lands.It shouldnt show any contact at those points.Also the carbon deposits that normally build up a piston can be Eroded away in spots if an engine is suffering detonation.
Can you take a pic looking down on top of the piston crown.
It sounds like you have a possible pre-ignition/detonation problem from what you have said.
Things to check !!!
Check your piston ring gaps.Worn rings allow a piston to rock excessively in the cylinder bore,allowing the piston to rattle !!!!!
Have you changed/advanced the ignition timing at all ??
Have you made any jetting changes ?

Premium fuel will not cause engine problems in a low comp engine it is purely just a waste of $ The only damage is caused to the hip pocket

Cheers Brian