Hi,
maybe I can help, since I have a similiar configuration and had the same problem.
Do you have the alternate NVIDIA driver installed ? It doesn´t work without.
If not, try this:
1. In Clover, load the config.plist of your EFI partition. Under "boot", set "darkwake=0", nvda_drv=1
2. Shut down
3. Plug your screen into the graphics port of the ASUS Z97
4. Boot and hit F2, to go to the BIOS. Switch to advanced mode.
5. Navigate to Advanced->System Agent Configuration->Graphics Configuration->Primary Display and set it to CPU-Graphics.
6. Save BIOS-Settings and boot, but stop at the Clover startup screen.
7. At Clover, choose "Options"
8. With the arrow keys, go to "boot args", hit RETURN key and type "nv_disable=1,nvda_drv=0" (this is temporarely and overwrites your config.plist just this time)
9. Hit RETURN key again and go back to Clover main menu
10. choose your startup disk and hit to boot
11. If all went fine, you should be able to enter your desktop. Now, get the right NVIDIA graphics driver for your system here:
http://www.macvidcards.com/which-driver-should-i-install-for-my-new-gpu.html
Also install the NVIDIA CUDA driver:
http://www.nvidia.com/object/cuda-mac-driver.html
12. Install and shut down.
13. Plug the screen into the card port.
14. Boot into BIOS, and set Primary Graphics to PCI-E
15. Save and boot into MacOS
16. Smile
Cheers
Oliver