Wett will send you a modified ECU with the new chip installed and your old chip in case you want to swap it back to stock. They bill your account an extra $1200.00 until you ship them back the original ECU so you have no down time. Or you can send them your ECU and wait a day or two till the work is done. In any case the chip in the modified ECU can easily be replaced. Be sure to tell them wether your car is 5 speed or tip it makes a difference.