I am using APam 2.5 on a EZ2, no airspeed sensor mounted. No matter settings I tweaked I could not make it to use 100% THR during auto modes(AUTO, RTL, FBW…). The only mode that the autopilot uses 100% Throttle is auto take off. I tried to calibrate the ESC, to change different values for TRIM THROTTLE, THR_MIN, THR_MAX, ARSPD_FBW_MAX and a few other related params but no success in getting 100% THR used, or at least 80-90 percents. With my current settings my EZ cruises at 27-50% THR no matter there is windy or a calm day.
What parameter should I try to alter in order to achieve higher cruising speed in automatic modes?
I finally noticed that using THR NUDGE has effect on cruise speed 
. Disabling THR NUDGE gives more flexibility to the ground speed that auto pilot uses. Of course, there is the possibility to dynamically change the speed interval that autopilot uses by nudging the throttle.