RX570/470 UEFI bios mod

HI,

I'll try to mod my RX570 MSI A and it's work fine BUT:
When I mod bios with polariseditor & atiflash (the proper version) Win10 don't detect GPU until windows screen (no windows loading) and I can't see the first windows desktop. No problem with stock bios.

Same with Sapphire RX470 8gb I can see windows boot with defaut bios but not with mod bios ! I think it's a UEFI GPU bios problem!

Any idea ?

Win 10 in UEFI mode (GPT partition)
MSI Z170 bios mod
4G Enable Gen 1
6 GPU (2xRX470 4xRX570)
2x1000watt PSU