I have a 2004 6spd cummins 4x4 and want to get the best MPG possible. Do you guys have any ideas. I have Edge and Diablo and only get bout 19mpg's. I heard bout The "Smarty" but wanted all you guys opinion. I have an '06 2wd cummins too and have a diablo and get 25. What is there out there for my older cummins?