AFR misleading? Plugs tell a better story?

Do you mean it is not losing a lobe ?
My thinking was it may be a poorely thought out grind.
It idles like a big grind but doesnt pull up high like a big grind . Kind of dies off around 5k... I-should have gone with the 800 AVS2 but I dont think that is the whole issue with the top end.
Just my 2 cents, but you may be running out of fuel on the top end.
What fuel pump are you using? Fuel pressure at rpm?