Hey EVH,
I would suggest to use Clover. Im also assuming that it is the intel version?
Install Clover (find 5108) with options on "Install Clover in ESP", "Boot Sector - Install bootaf in MBR" and "Clover for BIOS Booting - SATA".
Then replace the EFI folder with one attached. It has minimum kext to get things up and running.
Reboot and select the installer or hard disk to boot. I tested this with Mac OS Lion 10.7.
Regards.
EFI.zip