Just in case this helps someone...
I recently upgraded my motherboard, cpu, and ram, but kept the same 1050ti I had been using before. Previously, to get the video card to pass through, I had to disable HyperV and use the edited vbios method described in the method above. I also was already booting in Legacy mode, and had separated out my IOMMU groups so that the video card was in its own group. I also am passing through the audio portion of the GPU as the sound card.
After the hardware upgrade, I was again getting the error 43. After a few days of googling around and trying different things, what ended up working for me was actually REMOVING the manual vbios override, and letting it use whatever was the default. Not sure why this worked, but hey, I'm happy.
For what it's worth, I was upgrading from an old Dell t5610 with dual xeon e5-2680v2 (20 total cores, 40 threads) to an asus z390 with an i9-9900k. Good luck!