Reply To: If my piston looks like this, what went wrong?

[Rodney Ebersole]

You might look into the method you are using to get a clean plug reading, or ditch reading your plug and read the piston more. The lean condition can be in most of your running rpms and your rich plug reading is just while performing your “clean cut off.”
A cool day is great for making power unless your jetting is still set for a warm race day and 100 octane may work fine untill you run into a cool day with better air.