Thanks for your help, I appreciate your effort. I am running version 17a362a. I think that is the GM
I restored the original kexts and did a permissions repair. I ensured that csrutil disable was entered. I then installed only the modified 4250 kext. It doesn't load and info on the kext says it is not loadable and has a kext signature validation error.
I think I might reinstall High Sierra and start over
After a fresh install and updates make copies of the AMD kexts and put in a folder as spares to revert back to.
Text wrangler is a good free app for doing the edits or Xcode if you have that. The edits are fairly easy to do the key is running kext wizzard before reboot.
You can do it yourself and not remove the kext and hopefully avoid the issue.
Go to top tool bar and select finder, then drop to Preferences and open. Check the box next to Hard drives. Now your drives will show in desktop.
Click on drive to make edits and got to System>Library>Extensions and right click on the AMD4250kext. Select "show package contents". Open the contents folder and drag the info.plist to desktop. Right click on info.plist and open with text wrangler or Xcode and scroll to the area where you see the IDs 0x67FF1002, 0x67EF1002, etc.. and chenge one of those to 0x73001002 be careful not to change any of the spacings. Go to top tool bar and hit file>save.
Now drag the info.plist from desktop (edited) to the contents folder of the AMD4250kext and make sure you get the replace prompt, if you don't then hit cancel and retry it needs to go in the right place.
Run Kext wizzard, reboot and check.