Well, the only thing I can think of is that for some strange reason, your ECU is retarding your timing. Now why it would be doing that I donno. I would say that it detects ping but you shouldn't be pinging on the 101 RON and you said you didn't hear any... Perhaps the AFM does have somthing to do with it... I wish I could help ya out but I'm really at a loss. So my .02 is retarded timing. Or retarded ECU, or one on account of the other
Lemme know what you find when you get it sorted.