Crossfire Bad FPS. PCI Express bottleneck?

HI guys,

So I've been struggling to get a R9 280x CF to work properly, but I am about to give up. I think that my problem is that my motherboard has a PCI Express 3.0 at 16x but the other one functions at 2.0 4x when crossfiring.

I think that is why I'm not seeing the two 280x perform as they should. I game at 1080p, mostly BF4 and get 70-110 FPS on medium settings... :( 

What do you guys think, it the PCI at 4x bottlenecking my 2nd GPU so bad that I get these results? If I upgrade the MOBO will I get better FPS?

Rest of my specs:

Core I5 2500k
120 GB SSD
Gigabyte h67m-ud2h-b3 Motherboard

I appreciate if you can help me out here!

Yeah that second pci slot is killing it. Mine defaults to X8 for both my 7870's on pci 2.0 which is as good as it gets unless you go socket 2011 with the proper board. Overclocking your cpu might help as well.