Open Content Manager. Select "Content" in the upper right hand corner of CM. Then, go to the upper left hand corner and select CARS. A list of all your cars should show up running down the left side of your screen in CM. Now select the car that you aren't happy with, sound wise. You should see it's preview picture on the screen. Look at the bottom row of Content Manager. It should have options: Disable, Save, Delete, Find Information, Update Previews, REPLACE SOUND. Click that "Replace Sound" and it will pop up a new window that looks like the regular car selector when you want to drive. Select a car that you want to use it's sounds from.