I downloaded the current version of High Sierra from the app store and used a combination the current high sierra guide + this one
https://www.tonymacx86.com/threads/...orking-and-easily-affordable-customac.224812/
My install looked like...
- BIOS SETTINGS as per guides
- Use Unibeast to install high sierra (took 2-3 attempts as it kept freezing..)
- MultiBeast for post install (ticking apple lan for lan support - pretty much all I needed to do...) then a reboot and igpu started to work
- Voodoo HDA 2.8.8 direct from sourceforge install package and got audio working on the next reboot
Things not working include the aforementioned sleep issue and I still get random system freeze's, dont get any freeze's in windows so I've missed something out and I'm not sure what.
If your cpu has the intel 4000 hd built in then maybe run the install without the extra gpu and try install the gpu after.