I know you are looking for others to answer but I have given you the correct answer.
1question, Have you ensured your EGR system is functioning? Disabled or not functioning EGR can cause part throttle detonation
"Valve rattle" does not exist it is detonation.
Too much load at low rpm's will induse this in most cars that I have owned.
Just avoid the conditions that induce this and you will be fine.
Or get the tune changed to remove some timing in the bottom end.