You would need to hack your bios to get to that setting. ROG Hardcore posted up recently about how to open up hidden settings.
My question is why would you want to do this? If you are running more than 2 sticks of ram chances are it will not be stable regardless of what brand you are using.
I dabbled with this some time ago on my desktop machine and other than a very small gain in memory bandwidth benchmarks, like 5%, it amounted to precisely squat. Other benchmarks it did absolutely nothing 3D Marks ran 100 points higher once or twice but then it did that at 2T as well.
Careful messing with any memory settings in XTu. Last time I made a small change I ended up having to pull the laptop apart to get to the CMOS battery to recover. For the most part its best to just leave it at SPD and go with it. 2133 is already a nice step above stock.
“Two things are infinite: the universe and human stupidity, I'm not sure about the former” ~ Albert Einstein