I have had a RMS SC for over a year, w/ no problems and for alot less than Dian. The drawback includes the downtime, while they re-program the ECU and, of course, installation. Other than that, and gas mileage, I can't think of anything I don't like about my set-up.: Im thinking about putting an SC on my '99 M3 but im not really certain that i want to do it. does anyone know what problems are normaly caused by use of one? what is a good one that is not too expensive? im not nessesarily looking for the one that gives me the biggest torque and HP boost, but a good price and good quality. also what other mods will i have to do to support my new SC?