I had a similar problem. When I stepped on the gas (WOT) at say 3500 RPM it would misfire right around 5600 RPM. If I stepped on the gas at 2000 RPM, it would NOT misfire. I also noticed when logging that depending on when you jumped on the gas the AFRs were different.
The solution was to lower the throttle pump setting in the 3500, 4000, 4500, etc.... where ever I got misfires when I got on the throttle.