I have a 09>5,1 High Sierra SSD 850 evo through PCI Card slot 4. I installed a GTX680 - flashed for Mac. Updated to Bootloader to 188.8.131.52 Picked up a 970 evo on a cheap PCI M.2 adapter, installed in slot 3. I can see it, format it, install linux on it, copy files to it as a drive. But when I try to install High Sierra on it from my USB it fails, Installer says it fails and must reboot. I've tried to take my SSD/PCI out of slot 4 and same results. I also have a SSD in slot 1 of the drive bays with Windows on it and a backup storage drive in bay 2. So what to try to get OSX loaded on the NVME drive? New installer maybe? New Adapter.