my mod must have higher priority in the mod load order.
in addition with my Real Traffic density mod (see link below)
you can make sport cars as separate type of vehicles with own spawn rules by simply renaming the sii file from def/vehicle folder (base mod) into traffic_storage_sport.tm.sii
with this modification sport cars will have individual spawn rules from my traffic density mod and you no longer need other mods than my sounds and the base mod
Credits: Cipinho, TrafficManiac