fwiw... you may wish to look at this link providing information about using
obdII  management software to change auto computer  parameters

http://www.popularmechanics.com/how_to_central/automotive/1302786.html

they "discuss" reprogramming the car but leave it up to the user to locate
the information from the sources given.  Also requires a pass through device
which is kinda pricey,  but might be easy for a home electronics project.

hth

Peter