Bob, the closest a servo can get to linear movement is when the servo is centered, and the arm is perpendicular to the push line of the linkage. Not the Center line of the plane but the actuall linkage push line. The carb movement needs to match that movement so the carb arm needs to be perpendicular to the throttle linkage at the center point also. As pointed out by a couple of the otherpostershere, the mechanical linkage has to be right before any sub trim, end point or expo is introduced with the computer. Also, make sure the idlestop onthe carb is backed of so the carbcan fully close.. This mechanical setup is a must. If your carb is opening full at half throttle, the mechanical is way off, and it is highly unlikely that you can correct that with the computer.

Don