I found one way to reproduce the 'bug'.
I load my fav game, BloodRayne2, with my patch for FSAA (my vc++ project).
I start a new game, and i start to do 'alt-tab', between the game & desktop.
Each time, that i do alt-tab, there's an increase in the non-local videomemory usage of 6-7MB.
When, i reach 240-250MB (after 30-40 alt-tabs), there's a nice boost in the fps, from 90 to 100 fps (+-10%)
Just check my graph:
I've no idea, but it's a interesting bug.
I tried without my patch, with just the retail game, and same result.
If you do this process 2 times, the 2nd time, the system doesn't free the non-local video memory usage, and the boost is permanent, and the funny is that it works for all the games.
If somebody knows how to report a bug to nVidia, this is one that they really should investigate. A 10% increase in performance for free.