i recently straight piped an 06 cummins 4x4 q-cab, the owner told me he was averaging 13. 7 mpg before and now he is seeing 15. 1 on the overhead, all stock with an auto and 3:73s, is this a normal thing for the 06, he was mad because i averaged 14. 28 hand calculated, hauling his truck back from idaho, 200 miles, twins rock 
