Forza Horizon 4 not only offers a vast selection of over 700 vehicles but also allows players to upgrade and modify each car to some degree. This includes visual and performance parts that can alter stats like top speed, acceleration, handling, or even enhanced off-road capabilities. Typically, key upgrades involve changing the drivetrain (all-wheel or rear-wheel), swapping tires to significantly improve handling, and boosting or replacing the engine for more raw power.