all 07 and up have them and some of the 06 to in the 1500. some of the 06 had problems with it though. the 2500 and 3500 don't have them. as for tell when it activates you can feel a slight power shift between 4 and 8 cylinders, and if you have exhaust work done you should hear it to.
Hey guys, got a question for anyone that can answer. I have a 06 1500 which should have MDS from what i've read. I do not have an exhaust and i cannot tell at all when the switch takes place from 8 to 4 or 4 to 8. Is there something specific i should listen for when this switch takes place?