Downgrade EFI firmware to 1.6

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Unfortunately, you can't downgrade the EFI firmware unless Apple has released a firmware restoration CD for your computer model, not available for most recent Macs. If you try to do it, you may damage your computer, so I recommend you to take the Mac to an Apple Store or reseller

Far as we know, the EFI firmware can't be downgraded.

Run through this thread, apprantly there is something there related to your issue and a method (I didn't read it all, too much)

https://discussions.apple.com/thread/2054387?start=0&tstart=0

THANK YOU THANK YOU THANK YOU macieku. I searched all over the internet looking for that file.

This solved my issue with a Seagate Momentus XT 500GB in the 15" 2009 Macbook Pro (2.53).

Oddly, I have the exact same drive in a 15" 2009 Macbook Pro (2.66), and never had a problem with the 1.7 firmware.

Downgrading or installing anything into EFI firmware from a unverifiable source is akin to running malware on your system.

Any program or OS X itself can't assist in detecting malware in EFI nor can it detect outgoing transmissions or control as EFI sits between the operating system and the hardware firmware.

Programs can be installed in EFI firmware, so it's feasible a malware program is piggybacking on the unverifiable source of the EFI downgrade and thus giving the malware author ultimate control over one's machine, even more so that root itself.

I do not advise this course of action.