Do you think if i change it to the correct model, the graphics problem disappears?
I can't predict the future.
MacPro3,1 is not appropriate for laptops. See: http://www.tonymacx86.com/yosemite-laptop-support/146870-guide-native-power-management-laptops.html
So what can i do now?
I will make a changes to multibeast ? And try something else?
I tried all solutions, you suggested but none of them worked :\