tuning is done with either megatune or vemstune. until recently megatune as written by eric fahlgren for the megasquirt system was only option. megatune is licensed under gpl and can therefore be used by anyone. while excellent for megasquirt, it does not cover all aspects of vems, so complete setup and tuning is impossible. it can and has caused incorrect parameters to be written to vems causing unpredictable performance.