Check Engine Light P0300 [On highway Speeds of 75+]

[Nzeh]

When I get on the highway and I have the gas pedal all the way to the floor trying to go from 70 to 85 mph my [Check Engine Light] will start to flash. I managed to get the code while driving it [P0300: Random misfire on all cylinders]. My RPMS will stay at 5000 and will stay there but if I continue to hold the gas pedal down the truck will shift and then the [Check Engine Light] will turn off.