Original sentence: One of the main reasons that not all cars use KERS is because it adds an extra 25 kilograms of weight, while not adding to the total car weight, it is does incur a penalty particularly seen in the qualifying rounds, as it raises the cars centre of gravity, and reduces the amount of ballast that is available to balance the car so that it is more predictable when turning
Edited sentence: One of the main reasons that not all cars use KERS is because it adds an extra 25 kilograms of weight, while not adding to the total car weight, it does incur a penalty particularly seen in the qualifying rounds, as it raises the cars centre of gravity, and reduces the amount of ballast that is available to balance the car so that it is more predictable when turning