I heard somewhere that the 3GB 660 ti even in games such as Skyrim with high res textures that there is only a 1-2fps difference compared to the 2GB version. I heard that what was causing that was it's 192-bit bandwidth is this true?
It's much more likely that it's just not using all the video memory and the 1-2 frames differences is a marginal error.
the 192Bit bus only limits you after you go past 1080p or have some extremely high res textures.