1. You need to download EFI for your mac http://support.apple.com/kb/ht1237 (unless they haven't updated the page).
2. Be sure you downloaded right EFI, otherwise it could end up bad!
3. Get unpkg http://www.timdoug.com/unpkg/
4. Use unpkg on *.pkg with your EFI, then copy the folder you got to /Applications/Utilities/
5. Open copied folder, find a .scap file.
6. Open terminal, copy there sudo bless -mount / -firmware then press spacebar.
7. Drag .scap file to terminal.
8. Press spacebar and copy --recovery --verbose in terminal.
9. Press enter, type password and press enter again.
10. Shut down your mac from menu, wait until it will turn off.
11. Wait a bit, then turn on your computer but do NOT hold the power button down. The screen will turn black and remain in that state for up to 40 seconds. A gray screen will appear and a status bar indicates the progress of the update.