Downloaded “maps” are made to fit a specific bike (year & model) with specific performance modifications. In order to develop that “map” they used a specific bike with specific components and tuned it under specific circumstances. For example, a bike tuned in Denver would not be a good map for someone living in Houston.  If your bike does not “exactly match” the downloaded maps specs (which most of the time is very difficult to do because there are simply too many performance components out in the market), then the results will most likely be less than optimal. A Dyno-tune takes your bike with its new modifications and tunes it to work optimally for all parameters and load conditions for where you live.