Since I had searched a long time to get gfx string for my 8800 GTS 320MB (G80), I thought I post it here maybe it can be useful at some point for others.

I installed my Snow Leopard using the retail DVD.

I did not install any injector (neither NVinject nor ACLinject or GraphicsEnabler).
I followed the instruction to create gfx string. You can find a good one here (posted by eclau).

If you download my attachment you will see 4 files inside the zip file.
You should be able to just copy the com.apple.Boot.plist to your /Library/Preferences/SystemConfiguration/ folder, But first change it to your old boot.plist needs. If this method doesn't work and you want to follow the Eclau's instructions to create your individual graphics/network/sound strings, then you can start by 8800gs.hex or 8800gs.plist and just modify the sections that you'd lilke to. (Of course you have to follow what Eclau is telling you to do!)
8800gs.hex is my system's hex code that I pasted in com.apple.Boot.plist file.