X2 here I get 30 mpg's with the mds ON, off holy crap can you say suck gas???? and the transition is not noticiable when I am not using the diablo tune, but it is noticable(slightly) when the 91 tune is in, but is sure doesn't bother you, IMO only thing that leads me to beleve anyone that says mds is crap, might be do to it being on a truck, I have not driven a truck with mds, so maybe for that it is crap, but that is the only way to go on a car IMO. I have heard they are gonna put them on the 6.1 AND the 6.4 not sure about the 6.4 but I know they are going/or are doing it for the 6.1's