Black Screen after used Multibeast

Hello,

I had a nice El Capitan installation and I screwed up by using Multibeast to change my computer status (from MacPro 3,1 to MacPro 6,1). After I did it I got a black screen when it boots on clover, the apple logo even loads until the end and then I get a black screen. I know, I was so noob to use Multibeast... but anyway, I hope you guys could help me out to troubleshoot this.

Thank you so much!

My computer:
Gigabyte Z97X-UD3H
16 GB
i7 4790K
Geforce 780