MDS stands for Multiple Displacement System, which is a fuel-saving cylinder deactivation technology used in some Hemi engines. When the MDS system is active, it turns off four of the eight cylinders in the engine by shutting down the fuel injectors and collapsing the valves for the intake and exhaust with solenoids. This helps improve fuel economy and reduce emissions. The MDS system is found in some Hemi-powered vehicles, such as the Chrysler 300c, Dodge Charger, Magnum, or Challenger. However, some high-performance variants such as the 6.1L SRT or 6.2L Hellcat dont have MDS, and neither will early truck versions of the Hemi since fuel economy isnt as strict for trucks. If you want to temporarily disable the MDS system, you can do so by setting your gear limit selection to 8.