I would opt for the AEM system. It will take a bit more tuning time, but you will have control of when the second turbo comes on line, plus you can change ignition timing. You also have the ability to upgrade to larger injectors without buying anything new. The only problem I foresee on the AEM unit as well as any aftermarket computer is taking the time to fine tune the system. You may want to wait and see how the system works for other people once it is installed on their cars. I have a funny feeling many good used VPC's and GCC's will be for sale after the AEM computer is released.