I run the Futaba 3VCS
In the manual is says to set the EPA as :
1 Throttle (forward side) adjustment
Turn the throttle stick fully to the high side and use
the (+) or (-) buttons to adjust the throttle angle.
However, when using an FET amp, set to 100%.
I've always taken it as with ESC's ( ie FET amp ) the EPA is set to 100% to prevent overheating of the FET's due to not being allowed to apply full throttle