BSR's Protable Program Carrier (PPC) plugs into the car's On-Board Diagnosic (OBD-II) Port (where the mechanic scans engine codes) and re-tunes the engine computer. The engine computer can also be de-tuned back to factory settings. The PPC is married to the car that it first tunes (sorry, you can't pass it around).
BSR PPCs can result in significant horsepower increases (40-70bhp), espeically in turbo cars. The result -- really fast "Q-Ship" cars.