We now have an ARB-Legal TMax for our customers in the State of California! The ThunderMax 50 is a self-tuning closed-loop engine management system for 2001-2006 88” Twin Cam® bikes originally equipped with Delphi® open-loop EFI. The ThunderMax 50 installs easily and optimizes your engines’ tune as you ride. Because the ThunderMax 50 is a closed-loop system, the ThunderMax 50 ECM uses feedback data from the wide-band oxygen sensors and AutoTune module to ensure that the engine constantly maintains the optimum air/fuel ratio to maintain excellent throttle response, power and economy ARB Executive Order # D-644 - Requires addition of oxygen sensor bungs or an exhaust system with bungs. Click here to check out Zipper's products.