I drive a 2006 GMC Duramax, the best no cost enhancement I have discovered is to move the driver's seat very slightly more forward than your usual driving position. Doing so, allows the accelerator pedal to be comfortably depressed more. Makes all the difference.

are you sure about the no cost part? Seems it would use more fuel and that would in turn cost more.

No cost for the performance gain, not necessarily the results.

But....if you want to save fuel move the seat back a little so you don't press the pedal as far.