so its the servo that sticks, yes?
trial and error is the only way if it is not the servo..........take the ballend off the throttle and open the throttle all the way.....and then close it.......and then see if there is any 'rough' spots in the stroke of the throttle......if that checks out ok....then move on to the throttle servo......and move the servo horn with ur hands (radio off the whole time) and see if it sticks.....it thats ok try it again with the radio on (disconnected from throttle) if it sticks then u have a problem.......find out exactly where it sticks on the servo horn....take the horn off and position it bak on a few splines in the other direction....if u understand wat i mean., then try again and continue adjustin until it doesnt stick anymore...
or u could just replace the servo! standard futaba 3003 servo costs 20 buxs....
good luck
wog