HMF Engineering Gen 3 Optimizer 639552360001 The HMF Optimizer is a Fuel-Injection Controller that has been pre-programmed with the proper tuning specifications for your HMF exhaust. You must retune your machine when youre adding an exhaust system, so not tuning your machine will void the warranty of your exhaust Pre-Programmed with the best settings for your HMF exhaust Push Button Interface Unique load based technology Plug and Play Installation