If I understand correctly, the robot moves faster if the values of the ball sensor are low, and moves slow if the values are big. What is your strategy behind this behavior?
You also said that now you have more speed and power. Is it only because you added another wheel? Or did you also change the motors?
For example, if the ball is in the back of the robot there is a lot of back and forth movement, and conversely if the ball is in front of the robot there is a lot of left and right movement.