im not a 6.4 guru but in the surfing for a particular post that i did today i saw a few threads regarding bucking with the 6.4. some of the things can be tuned out by a aftermarket tuner as well as mpg restored thru tuning. im am a skeptic on gaining mpgs from a tuner though. take a look twards the bottom of the page there is a specific spot for the 6.4 which is the diesel you have. i would also look into the spartan tuner. i can shoot you to a few different sites if you want just send me a pm