Friend of mine has been doing that for years. He gets a new car, then goes to China and gets software installed in his laptop for that particular car.
He changes whatever he wants; mainly the engine performance and gets a lot more horsepower out of the engine.
He had a big 4-door BMW that would burn rubber like crazy. He changed the exhaust system, changed the computer chip in the car and then tweaked the engine to make the car a super bad BMW.
` The Car Hacker's Handbook might be of help.