I've spent some time going through Roger and Mechanicman's posts, and now I have a few quick questions. When talking about a 20/20 tune is this 20% fuel added and 20% timing or boost added? As for timing goes, correct me if I'm wrong but more timing (to a certain point) = more mpg/power correct? Why then do the example calculator tables show a lower number in the cruise area than the stock table? I have an 08 LMM that I am looking to just add timing and possibly 5% fuel or less. I don't need another rocketship, I just want driveability with some more bang for my buck (MPG's). I am familiar with LS1 HPT stuff and am familiar with the older cummins stuff (VP44), but this whole duramax thing has me a bit confused . Any insight into this would be helpful. Also, could someone clarify exactly what the timing calc does when you enter 50%? Would this be like adding 50% to the table or what? Thanks for your patience in advance!