If you are running your I7-920 at its stock 2.66GHz, that means that the bus frequency is 133 MHz.
Your RAM is running at 8X that, 1066 Mhz.
You don't say what your motherboard is, but there may be a BIOS setting that allows you to set the RAM multiplier up to 10, to get 1333 MHz. I suggest that you set the RAM timings and voltage to their nominal values. If this is your RAM: XMS3
it's 9-9-9-24 at 1.5V. (The page also tells that if you rely on the SPD seeings, you'll get 1066 MHz.)