12-13 HARLEY FXDWG: Vance & Hines Fuel Pak Installing a performance exhaust system is only your first step. Now, you need fuel management. You need Fuelpak. Your fuel-injected motorcycle is equipped with an ECU (electronic control unit) that's programmed to deliver fuel to the motor based on an air / fuel ratio for a stock air filter and stock exhaust system. While the ECU can self-adjust for environmental factors such as temperature and altitude, it can't adjust for mechanical changes like adding performance parts.