if your not able to boot or install Yosemite
Set boot flags to -v -x nv_disable =1 GraphicsEnabler=No using Chimera boot
if you installed OS successfully, then download and install the web drivers, after installing the drivers it will ask you to reboot, once after rebooting nvidia icon will appear near time(Top Right corner ) click on it and change it to nvidia web driver and reboot.
Nvidia web drivers Mac OS X Yosemite
10.10 : http://www.nvidia.com/download/driverResults.aspx/79077/en-us
10.10.1 : http://www.nvidia.com/download/driverResults.aspx/80070/en-us
10.10.2 : http://www.nvidia.com/download/driverResults.aspx/81365/en-us
please feel free to contact me back.