I like the Cummins and many of my friends have it, but exactly what year Cummins had more power than ANY year Duramax?? I remember shopping for trucks and the Cummins was making like 250/490 to the Duramax's 360/650....
Or am I missing something here?
And I have heard stories of LB7 (1st gen) getting near 30 mpg on the highway once broken in, and I myself pulled a consistent 18-19 mpg in CITY driving with a fully loaded 4x4 and a race tune.
Anyways good luck and hopefully HPTuners will be able to help you out in the future.