02-11 HARLEY FXDWG: Vance & Hines C.A.R.B Approved 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. When you install a performance exhaust system, your airflow changes, so you need a fuel management system that adjusts your air / fuel ratio to match the changes.