DHG#1302 a custom chip is to make your car perform better with additional mods that you might have made. In my case, I have long tube headers with an off-road H-pipe 3.73 gears and once the car arrives I will be mounting 18" Torque Thrust II's on her. Additionaly, I will be using premium fuel. Because my car is naturally aspirated it will still run without the chip, however, a correctly programmed chip can maximize the performance of those mods. Also because of my gear and tire change the only way to get a correct speedo reading on the car is with a chip. There is a box that you can buy which plugs into the coomputer harness however, I have been hearing negative things about it. As for the stock chip, basically it just allows you to use premium fuel and for cars with automatic gearboxes it usually provides better shift response. Unless you find a chip tuner who absolutely knows what there doing and offers free upgrades when you upgrade I would only recommend that you get one after you have made your mods. By the way if you ever supercharge your car you must have a chip and heed this warning, only get a chip that has been programmed while your car is on a dyno.