I had the very same problem with my previous build. I was forced to remove my GTX 1080 until I changed my mobo. After that it worked. I'm not sure if it was the Motherboard or whatelse, actually I've upgraded all my system. Btw I'm not using Lilu.kext neither nvidiafixup, I've just AGDPFixed my AppleGraphicsControl.kext, Lilu gave me some problems in the past. EDIT: I'm using MacPro6,1 as SMBIOS, dunno if it can help or not.