Im a snowmobile mechanic and I know how to build HP out of a 2 stroke! But in a 4 stroke about the only thing I know of is to increase stroke to make more torque? I plan on reworking my exhaust manifold (unless some one makes a header for the Suzuki 660?) And have been toying with the Arctic Cat 660 motor that makes 80hp stock! But have hit dead ends when it comes to anyone knowing what all is different? So how do you make torque? Not as concerned about top end HP!