here is screenshots of both process explorer and in game with the OSD listing vram usage at 1920x1080. 1991MB is pretty damn close to 2GB and doesn't leave a ton of room. Vram is totally an issue for sure. This is why I was saying I wish I didn't buy 2GB cards in other threads, but since I bought at launch I didn't have much choice. When you get to that point the stuttering starts. Before that is it 100% smooth. 2560x1440 goes up over 2000MB and stutters very often when it gets up there. So I don't know how else to explain what I see with this game. When it's below 1900MB even at 1700-1800 the game never stutters. The second it hits 1900MB (roughly 1.9GB) it stutters and the fps drops. This isn't the engine stutter, it's something else. If I go down even further in resolution or drop texture settings I don't see the same stutter.
Maybe you can explain what I'm witnessing without blaming the engine when it's clearly not the UE3 engine itself doing the stuttering. Perhaps Bioshock Infinite is just coded poorly in some way? When the game first loads or you are inside someplace, and see 1300-1600MB vram usage the game never stutters even once that is noticeable to me. I always have vsync off so there might be some tearing, but no stutter. When the vram usage ramps up the game physically pauses on screen. Usually less than a second's worth but it does get annoying when it does it often enough.