Manufacturers often use the same engine in a series of vehicles but allow certain models to achieve their true power so they can retail at a higher value. This is a marketing tactic employed to make you spend more. Manufacturers also have a wide range of rules which they must adhere to so they can produce their cars. These can range from specific emissions tests to which fuel grades an engine utilises. Ensuring they meet these requirements is vital for manufacturers, and therefore stock engine performance tends to be lower than what it can capably handle