ok im not a engineer but the son of one! however the exhaust will just improve your air intake, the air intake will not significantly improve your top speed. However it will improve your 0 - 30mph or 35 if you want to break the thing. Put it this way...... a 50cc moped is a 50cc, don't bother modding it up, it will only end up making it illegal as a big bore kit will only increase your cc which makes it illegal, which also voids your insurance. Just live with it for a year and get a 125.... sorted!