I am not sure if I can help you. I have a PC set up with two GTX 460 connected with an SLI Connector.
In Windows 7 (booted from a different HD) I have SLI without a flaw.
My Maverick 10.9.5 Installation recognises BOTH Graphic cards but apparently they are NOT in SLI modus. I have one Monitor connected to each graphic card Both Monitors are working as they should (expanded display). It is not necessary to remove the SLI Connector in OSX. However I think SLI is not possible with OSX 10.7 or 10.8 or 10.9
Intel Z68 Motherboard with I7 2600K Sandy Bridge Processor not over clocked
Realtec ALC 982 Sound
Dual Intel PCI Ethernet/WLAN/Bluetooth/FaceVsion N1 Cam
Eye TV Hybrid Digital and Analog TV
16 GB RAM
2x GTX 460 Graphic Cards, 2x 2412H Displays
120 GB SSD
2 TB HD
Clover Bootloader 2953