bob16314
K-Boost will lock the core clock at it's maximum boost clock speed resulting in higher temperature and increased power consumption and generally isn't recommended unless it helps with benchmarking/game performance issues, but it won't hurt anything..It's much more preferable to create a more aggressive custom fan profile using PrecisionX or MSI Afterburner and/or set the Power management mode in the NVIDIA Control Panel to Prefer maximum performance like Arestavo said.
 
The Prefer maximum performance setting will not allow the core clock to drop below it's base clock speed, but yet still allows for full boost clock speed when needed..You can set Prefer maximum performance either globally in the Global Settings tab in Manage 3D settings which affects all games/3D apps, or on a per-game basis in the Program Settings tab which will affect only the selected game..If your game isn't listed in the Program Settings tab, you can add it by browsing to the game's executable.

Sajin
Flashing a custom vbios onto your card that has boost disabled is another option.