Adjusting your tuning when changing out your exhaust system is good practice, as it ensures a fast and responsive motorcycle. With modern, fuel-injected motorcycles, ECU tuners for Harleys make tuning your motorcycle a breeze. They plug in to your stock wiring harness and connect to a smartphone for on-the-go tuning for maximum horsepower and top speed! For carbureted bikes, changing the carburetor jets to add or remove fuel from the throttle range allows precise tuning for optimium performance.