Sound like the engine torque is rolling ya faster to the right then the left. AS mentioned before measure the acual throws and check for control rods beding on the rudder. Pull pull stsems will remedy this.
other wise to see if it is really the engine try useing a smaller diameter prop with a larger pitch. carefull because the plane may travel faster though it won't have the pulling power. if the roll rate if affected less than its youe engine doing it. Oh and put the original prop back on. the planes ment for aerobatics not speed
