some people will map on the road, for "real world" figures. so your not in a stuffy rolling road room, with a huge fan blowing more nice warm air across it you would probably get more of an aggressive map being on the road. the tuner will hook his laptop and air/fuel reading equipment up to your car, then map on the road. with either you driving in each specified gear , and at the required speeds. obviously slightly illegal speeds needed... then most mappers will put it on the rollers for a power graph where they can see the maximum output.. cant go ripping top speed up the road can we the boost controller is simple if you have a clue what your doing.. if not then leave it to a pro, it will be a 15 minute job for him whilst hes wiring/mapping the car.