On the x97 mb with m.2. pci-e slot x2 you will never get the speed of the new m.2 pci-e x4 slots!
The GB X97 mb's do not have the new pci-e X4 m.2. slot, this was introducted with the z170 series.
As already advised I did it my self, the workaround is to use the de-lock add on card place it in the bottom
pci1 x4 slot this will allow your m.2. ssd to reach max. speeds.
However if you sli gpu cards don't allow you go for this option space wise, you are stuck with the top m.2. pci-2 x2
slot max read approx 950 / 1000 mb/s.
My 950pro on the z170x gaming 7 runs as at max write speed of 925 mb/s read 2200 m/bs