difficult to see the effects of an individual load site when timing runs, so although it may help if you move the whole curve up and down, it is unlikely to allow you to optimised the shame of that curve.

Can you show me an AFR plot too?

Its just that based on what you have said about helding a steady 12.6 AFR and the power dieing off over 4500, that fuel map isnt what I expected to see at all, I was expecting to see the rate of fuelling decline as you approached higher rpm, to signal a drop in VE.