Most cars when you open the folder up you will see the folders Meshes, Scripts, Textures (May Be More), anyway go to Scripts, Then SRC (If there is no folder named src you can't edit it) look for a file named CAR_VT.java, scroll to the bottom and make the prevalence higher.
P.S SRC stands for source files.
P.P.S if there is a double slash like this // then it means to skip that line. If it's there remove it.
EDIT: SRY for late rply