My advice, don't.......yes, it'll probably get better milage and have more power with a programmer, but durabilty of the drivetrain will suffer. I bought a 08 Dodge 3500 4x4 in March. It has about 4500 miles on it now and I love it so far, no mods at all. I only use it to tow, It has more than enough power to easily pull my 8000-9000 lb trailer over two 12000-14000ft mountain passes at 65mph on cruise and still get 12 mpg. Granted the older Cummins got better milage, but I'm not willing to take any chances with durability.....jmo
Johnny