HELP please - Ati 2600xt mac efi64 bios

Hi,

I've a problem with the original ATI 2600XT mac version (in macpro 4.1), my friend have flash it with windows firmware and now my mac don't recognize it.

I tried to flash it with many firmware found in internet but not works (always black screen).

Please tell me how I can find right bios (with efi64) and how I fix it for use again in my macpro.

Thank you.