I just got the SCT X4 about a week ago. I got Unleashed to do a custom e30 tune with firmer shifts. Absolutely love it. easily chirps second gear and gets a little crazy in sport doing a pull. From all I have read, Livernoise and Unleashed both seem like good quality tuning companies. I would not do a piggy back system since it tricks the ECU into reading something that is not there and you can tune transmission and a lot of other smaller perameters.