Not sure if I ever posted here and if then for sure nothing else than question, so I am lucky to finally give something back to the community.
I did a maintenance of my home server and decided to finally use the empty PCIe slot.
I could have just added the NVMe disk as additional disk which might have been enough for the VMs to run faster, but I wanted more. 
There wasn’t any mod of this particular BIOS, so I have decided to try to do the mod of this 7year old MOBO myself.
The PCIe-SSD is the Samsung 970 PRO NVMe SSD.
I have used this PCIe adapter h t t p s ://axagon.eu/en/produkty/pcem2-s
I followed the guide on h t t p s ://w w w.win-raid.com/t871f50-Guide-How-to-get-full-NVMe-support-for-all-Systems-with-an-AMI-UEFI-BIOS-388.html up until the step 4.
I have used the UEFITool_v0.28.0 and after opening the original BIOS I could see a message “parseBios: one of volumes inside overlaps the end of data”.
But the step “3. Insertion of the NVMe module” completed without any message and there was enough space in the “drivers” volume (arround 200kB) though, so I have used the NvmExpressDxe_4.ffs.
I was able to successfully flash the BIOS via the EZ Flash tool which is part of the BIOS.
The only glitch was, that you have to use a black USB 2.0 port, the tool didn’t see the flash disk while being inserted in USB 3.0 port.
The same is valid for Boot menu, it will not find any bootable disk, it looks like this BIOS might benefit from some other tweaks for example USB3.0 drivers.
I have also thought about updating the storage drivers, but I wasn’t able to follow the guide, I couldn’t find the right GUIDs so I ended up just with the NVMe module.
I have used the Paragon suite to copy the partitions from the original SATA SSD to the new NVMe disk.
After that it didn’t want to boot, it wasn’t able to find a bootable disk.
So, I booted the Paragon once more and copied the EFI partition again and this time checked the checkbox something like “change the EFI to boot from this partition”.
After this it booted from the NVMe disk, but I could see another error about not being able to find winload.efi file.
I have booted again the Paragon boot disk and used the Command prompt to:
- run diskpart and assign letters to the EFI (S:) and Windows (W:) volume
- run “bcdboot w:\windows /f UEFI /s S: /v” command to create correct BCD entry
- run “bcdedit /set {default} safeboot minimal” to make the windows to boot to safemode so it enables the NVMe driver inside the cloned windows
- run msconfig and remove the safeboot checkbox and restart, alternatively you can use the bcdedit and remove the safeboot entry
After this final correction everything works as expected.
EDIT: One additional thing I did is I have installed the latest Samsung driver from the thread h t t p s://w w w.win-raid.com/t29f25-Recommended-AHCI-RAID-and-NVMe-Drivers.html#msg61 I took the “pure” 64bit Samsung NVMe Driver v3.3.0.2003 WHQL for Win10 x64 version
Thanks for the great guide and tools I could use to make it happen!
The MOBO is following one h t t p s ://origin-w w w.asus.com/Motherboards/P8H67I/overview/
The original bios P8H67-I-ASUS-0907.ROM can be downloaded here h t t p s ://dlcdnets.asus.com/pub/ASUS/mb/LGA1155/P8H67-I/P8H67-I-ASUS-0907.zip
The modified BIOS P8H67-I-ASUS-0907-modNVME.ROM is attached to this thread.
I hope it helps someone 
PiGeon
PS: I had to obfuscate the urls, I hope I will have more posts soon to be able to fix it for you, or maybe any moderator can fix it for me.
P8H67-I-ASUS-0907-modNVME.rar (2.17 MB)