A bad ground to one of the electrical components could act that way. I chased one of those for a bit a while ago...
Check the connections on all the slide on
electrical connectors for corrosion
Higher RPM demands more current to fire the coil and ECU which can lead to high resistance connection going open like a switch turned off
Higher heat from more current flow has more resistance
Something on the ignition side is going open when held at WOT under a load long enough to create this problem
I've seen this before years ago on a race car that was stored inside from PA