Eduardo, if your're referring to the latest Mac Mini version, bear in mind that it is the Late-2014 model -there is no 2015/16/17 version-. You can refer to my thread, there I mention the exact config I'm using to add a standard (non-Apple branded, nor used) new PCIe SSD drive, to the factory HDD: PCIe SSD on Mini Late 2014 Regards!
Hello! please refer to this thread and comments added on it, as I have been able to add a Samsung PCIe drive successfully with the proper connector and adapter: PCIe SSD on Mini Late 2014
I’m still looking for the correct way to make my own Fusion config.
@non_belieber I think I can assist you on what you’re trying to upgrade; please contact me privately, and/or review my thread related to the PCIe addition on a Late-2014 Mini. Regards!