[Dominik]

If I understand you correctly, your ping occurs at high rpm only. Not in the 1500 to 2700 range when you accelerate.

If it didn't ping on the dyno, I suggest to retard total timing by 3 degrees to countereffect the heat under the bonnet (more heat than on the dyno).

You then may have to bring the ignition advance back to come in a bit quicker in the 1500 to 2700 rpm range.

This is not easy to be done by a novice on the street with loud sidepipes. It's a job for a new dyno run while you monitor the power drop and AFR.