just a quick clarification... HPF does not re-tune or re-flash the DME. They use their HPF Engine Management System(EMS) to control fuel and spark and the factory DME maintains control of TPS and idle functions. They use AEM engine management software for tuning their EMS. This could be considered a stand alone system except that they allow factory DME to maintain some functions of the car. This allows the car to be returned to full stock configuration if desired without hacking up DME wires. This setup would allow a very easy tune to the Z4 M especially with their master tuner. The problem is "supply and demand" economics 101
and getting the hardware to fit in the perfect place..which cost money boys. They are considering a Z4 M project within a year and that will require a loaner.