What is your card's device id? You can see it in System Profiler. If its already in that list you dont need to edit the plist of NVIDIA kexts, you would only need to do that if your card's device id its NOT in that list.
Using chameleon GraphicsEnabler requires you to know what is the device path, it can be pci0 and pci1, if you are using the wrong one it wont work.
If you get the EFI String working it could be its not appropiate for your card, being a laptop card you may need to play with nvcap value inside the string, what is your laptop model and how many video outputs it has?
Alternatively you could try using a kext injecter like
nvenabler, maybe you would get better results, you would need to run Snow in 32 bits for a better chance of them working, though I think nvenabler supports 64 bits now.
Any method you try remember it needs to be only one in effect, i.e. if you use an EFI string you need to disable GraphicsInjecter and not have any injecter kext like nvenabler and the like...