7970 X2 (OC) PCIE 3.0 X8 VS X16

G'day,
I'm just curious to know what you guys think on this issue.
I'm wondering if having my 2 MSI 7970 Lightning cards (1200/1700) running at PCI-E 3.0 X8 is a bottleneck by any sort.

When running 3DMark11 and running it at absolute max settings, the gpu utilization is as follows:
GPU1: 91-98% (Ranges)
GPU2: 99% (Solid 99%, never moves)

This is utilization when using a resolution of 1080p as well, 1 monitor.

So basically, if I was to have, lets say, a monitor at 2560x1440 and a monitor at 1920x1080, connected, would PCI-E 3.0 8X bottleneck my overclocked graphics cards at all? By 1%, 5%, 10%, any major difference?

Thanks!