Some obvious things I've learned in the past that improve hp include going to electric fans, pulleys, intake/exhaust. Since they don't make pulleys someone could always take there set off or buy another set of stock pulleys and take them to a machine shop and have a custom set made out of whatever metal he or she chooses. Fans are easy-ish. Intake and exhuast can be custom made. Its all in how how deep your pockets are.