We finished the program for the 135i/335i and 535i earlier this year. The results on 135i/335i and 535i are amazing, I have attached a picture of a 135i on a dyno in Germany hitting 174mph at 6100rpm. We took this car up to 197mph!!! Singh Autosport has never been a promoter of 'piggy back' systems. We would rather read and write a new file for the car. Tuner's with limited knowledge will tell you BMW can tell if its been programmed and will void the warranty, piggy back is the best way to go, blah, blah, blah. BMW is actually one of our biggest customers, they understand exactly what we do.
The car is programmed via OBD2 and can also be bench flashed.
(The reason why the dash lights are on is because the picture was taken on a dyno).