Here is something I dont understand. For some vehicles you can get a chip that gives you around an extra 10 MPG plus a little extra horsepower (it has been proven it works). How come this technology isnt used in vehicles in a daily basis?
Im willing to bet the car and oil companies are all chummie to not include them to keep oil demand high and fuel prices up
this one's pretty easy to answer(although mr kgb will be along to tell me i'm wrong

)
use a ford focus for example. this car is mass produced. it has to meet emissions standards in every state, plus it has to run good at higher altitude places as well as sea level places. it has to run good in cold weather, and hot weather, on many different qualities of gasoline.
to do this effectively, and affordably, they use a program that makes compromises in order to achieve this.
there were ford racers back in the 80's and 90's cracking the code on fords EEC4 control systems, and gaining upwards of 50hp by simply changing the fuel and timing curves.
so now, imagine if you could write a program for your computer changing the injector timing, the injector "on" time, the ignition timing(EEC5 and most obd2 systems can actually control ignition timing individually per cylinder), and so on.