Hi, I suffered from decel ping/ knock on my 2018 300 that I couldn't seem to jet out. Checked the comp ratio and it was 13.85:1 std. With high sqish. Fitted the S3 head with highest comp black insert which reduces comp to 13:1 with reduced squish which cured my running problems. I have been told that the std 19 head is lower comp STD. I'm in the UK and suspect that different fuels across the world will have different effects .
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