Flashed successfully using a USB with FreeDOS and AFUDOS v3.06.01 from >this thread<.
Prepare a USB with FreeDOS (easily created with Rufus), copy AFUDOS executable and the modded BIOS file to the root of the USB and then boot from the USB.
After booting FreeDOS, type the following commands:
AFUDOS AM1M-A.rom /O
AFUDOS AM1M-A-ASUS-1501-NVME.rom /GAN
Now you should be able to boot from PCIE
SHA256: 866B71D7393AEF7B9D762E165235A61713A98998AB2AFCB1DD355A1B6060B56D
Size: 8.388.608 bytes / 8192 KiB