Ok, I'm almost there...
As I posted before I was having problems with my graphics card, and was able to boot the computer by removing "nvda_drv=1" fom config.plist but that did dot fix the refresh problem, reading and looking I found out that some guys had problems with the same card using "Maverics", and some had,had success changing the Mac profile.
So I did the same thing, changed the profile from MacPro 6.1 to 5.1 and edited config.plist accordingly.
And voila !! (I'm attaching a copy in case someone has my same problem)
The computer boot and started to work "almost" perfectly.
The only problem is after sleep, that the audio goes away, although that is a known issue, I have a question...
Using Multibeast 6.1 to change the audio driver.
Should I use "With DSDT" or "Without DSDT" ?
(it's WITHOUT)
(quote from original post)
"NOTE 2 (written on 01/13/2015): Current MutiBeast AppleHDA.kexts lose audio after wake from sleep in Yosemite. The audio kexts from MultiBeast 6.1.0 don't suffer from this problem. However, this older kext may stop working in the future. I recommend trying the version from MB 6.1.0 first and if it doesn't work for you, or stops working after future OS updates, try the newest release. And remember, you must always reinstall your audio kext after updating the OS. Also, If you already installed a newer version in the steps above it's OK to run MB 6.1.0 now. It will just overwrite the last kext installed."