iMac 21.5" 2011 no EFI boot screen

[microitech]

Hi everybody, I replace a fried GPU on a 2010 21.5" iMac with a 4670 purchased on eBay.
It's working when MacOS it's loaded but don't have the EFI boot screen, I try to install OCPL on internal HDD but still the same. Then I had download a 4670 ROM from the web and flash it through linux.
Now on "about this Mac" show me that the card its an ATI HD 4600, don't know if the rom was wrong or what.. but I still have the issue.

What can I do?

Thanks

 

[AlixSPQR]

Perhaps this can help? https://www.rodsbooks.com/refind/

 

[microitech]

Perhaps this can help? https://www.rodsbooks.com/refind/

Unfortunately I can't boot on recovery to disable SIP. I move to left with keyboard and press enter but its stuck on black screen. Before flash Vbios I was able to boot on recovery. If someone can upload 4670 VBios dump I will appreciate.

 

[microitech]

I had dump 4670 firmware from another iMac, but now I'm unable to boot the faulty Mac from USB. I press alt at start, move to right and press enter. The Mac its ON but the screen stay black and on list of devices attached to network I can't find it.
What can cause that?