*************IMPORTANT************* --before attempting to increase your GPU voltage, try the following:
1) Clean the dust out of your computer. Dust causes your computer to overheat. I recommend un-mounting (not unplugging) your fans and cleaning the fans and heat sinks. You should use some combination of a brush, vacuum, and compressed air.
2) Update the driver for your GPU.
3) In your nvidia control panel go to "Manage 3D settings" and for "Power management mode" select "Prefer maximum performance" instead of "Adaptive"