All the above is true and will help. But you can still screw the system up and defeat the system if you don't follow one very simple rule.

When the throttle stick on your transmitter is at 50%, the angles your pushrod makes should be at 90degrees to both the servo arm and the throttle arm. If you haven't rigged the system to do this, you've probably killed the carb opening/closing properly in one direction or the other.

If you don't setup the pushrod to the servo arm, and the pushrod to the throttle arm correctly, you start off in a lose lose situation before any of the other advice can help.

Start out with the transmitter stick at exactly half throttle. Set the throttle trim at center. Now hold the throttle so that it is half open. Or half closed if you're a "half empty glass" kinda guy.

Now route the pushrod so that it makes a 90degree angle with the throttle arm on the carb. The arm can be loosened on the carb and tightened at that right angle. And should be. You want the throttle opened half way with the throttle arm at a 90 degree angle to the pushrod. If you don't have that right angle, then when the pushrod pushes or pulls, it's going to not have either enough push or enough pull. Yeah, the pushrod will move back or forward enough, but the throttle arm has a rotary motion, and it won't be moved "around" enough in one of the two directions.

Same thing is true of the servo arm. The servo moves it's arm in a rotary motion. If the pushrod isn't at a right angle to the servo arm when the servo is sitting at 50% throttle, then the pushrod isn't going to be moved equally in both directions.

If either the servo arm or the throttle arm is NOT at a right angle to the pushrod when the servo is at half throttle and the carb is half open, you can wind up with what you're seeing. And no computer radio in the world can do anything about it if it's rigged badly enough.

Just last week, one of our more experienced guys who has been flying A LOT for the last 4 years had a newly purchased airplane that wouldn't throttle right. No matter how he set the endpoints or changed the centering in the radio, he could not get the TX stick to open the carb completely. I heard him say the only solution was to swap out the carb. It was an effort to convince him to let me adjust the rigging. The EPAs had to be brought back to 100%, the centering centered, the stick put to 50% and trim centered. At that point, the servo arm was about 3 teeth off and the throttle arm on the carb was about 50degrees from a right angle. That carb had no hope of ever opening fully. We set the servo arm to a right angle with the pushrod and unhooked the pushrod so we could adjust the throttle arm at the carb. Held the carb opened half way. Set the throttle arm at a right angle to the pushrod and tightened it up. Tightened the pushrod at the servo arm and were good to go.

After all those words........ this may or may not be your problem. But it often is. And worth a look.

................edit to add pictures and description.....................
The picture on the left shows a smaller (weight consideration) throttle servo by itself to the right in the picture. It's servo arm isn't exactly at 90degrees but is close to it. (I setup the throttle on some models to give linear power advance, not just work linear. So center stick on the TX doesn't usually wind up being a good example of this topic.) The picture on the right shows the throttle barrel opened about halfway, and the throttle arm is about 90degrees to the pushrod.