I have a good news. I've updated my firmware mp1.1_005D_B00 to mp2.1_007F_B06.0709141354!
I want to explain cleary (... I'll try...) how I did it and also I want give you the patched file too.
The main idea is to modify the MacEfi program to recognize the damn fw version. So I spent one hour to understand how it works 'till figure out how it patch the original EfiUpdaterApp2.efi to deceive the update process.
It works with the "
patch" command line and a patch file that contains the modification to apply on EfiUpdaterApp2.efi. I only modified the patch with our (damn) firmware string.
If you want update your fw just download my patched version from this post.
I hope MacEFI does not mind about my mod on his program.
Let me know if it works for you too. Have a good we folks

P.S.This modified version only works on firmware mp11_005D_B00.
0709141354. This strange firmware was released in many different dates (mine is 0709141354). So if it doesn't work, please hex-edit the "MacProEFIUpdater2006.patch" file (inside the .app) with your fw release date (you can see it with geekbench on benchmark report screen). However you can find, down this page, a new updater tool version that supports more release dates:
0709141354
0708280936P.P.S. The last modified program (working on
0709141354 and 0708280936) should works for downgrade process too (but i never tested it). Remember to reset PR-RAM after the first reboot with your new firmware otherwise the profiler only recognize one processor. (cmd+alt+p+r on boot)
P.P.P.S. I don't know if the fan's behavior was the same before the upgrade but, with new firmware (with native support for my new cpus), on a stress test condition (10 instances of terminal running "yes > /dev/null" command), my E5345 Xeon couple reach 57°C and the cpu fan increase his velocity from 500 rpm (standard) to about 650 rpm. So the SMC behavior (that control the fan's rpm too) seems to be normal.
Antonello
Thanks MACEFIROM, thanks all!