Our systems are similiar.
4.09 doesn't seem to run quite as smooth as the others - particularly in the heavily treed mountains and over the cities. You micht search my posts as I have proveided some detailed analysis. I don't like the perfect cloud settings so I don't use it.
1. If you are using LCD absolutely leave VSYNC on as LCD can only present in effect 60 FPS mas. Due to implementation higher FPS and vsync off might not appear as artifact free and smooth as with vsync on.
2. I allow my E8400 to multithread with both cores as setting processor affiity for IL-2 to a single core does not seem to improve anything.
3. I have tested all but the most recent unified drivers and I stick with 174.74 as it seems to be the best/smoothest/least buggy for me.
4. In NVIDIA GPU controls I have AA and Ansi all maxed out.
5. Try with one card, maximize all settings to see if it is smoother, perhaps SLI has issues.
6. I sense Senior FLYBY is lurking and will show up soon!
PEACEs