Copy handling.meta to a folder and make sure to make a backup. (Or use the one I provided)
4a. Copy the code I gave and place it into the code of another car.
4b. This is explained in the jpg picture but go down to 'AVERAGE'
5. Now rename the handling.meta file to handling.meta if it isn't already.
6a. Then copy your modified handling.meta into the folder you got it from.
7b. Make sure to enable edit mode.