asus K72JK, rebuild efi bios

hi,
I'm dealing with a K72JK with a bios problem (bios update gone bad)...... no sign of life.
So i disassembled the pc, de-soldered the bios chip and reprogrammed with the bios file from asus web site.
Now when I plug the power cord it "start" itself for 1 sec (i can ear the fan spinning and the hd turning on) and turns off, after 30 second it starts again but there is no boot , no hd activity, black screen, actually only the fan spinning.
Holding the power button i can turn it off, and if i press it again the notebook start a sort of boot-loop, where the fan and the hd start and stop.

This laptop has a EFI bios, in fact the file i read from the chip is 4MB, but the file from Asus web site is 2MB, do you know how can I rebuild a good flashable file?

thanks