Holley sniper efi

You have just started a VERY long argument LOL.
Whether you are happy with any EFI is going to be how it is installed and whether you have an grounding/ ground loop/ RFI/EMI problems, etc etc and whether you can program it. It might be "self learning" for the fuel map but that is certainly not the complete picture.

I WOULD CERTAINLY want to "rig" that system up and verify that it powers up and seems OK before you buy it. That would be a GOOD buy if it is complete. And works