Your system is not to different from mine(I'm on a laptop, I'm assuming yours is a desktop) - I used the bushes removed, grass removed and tumbleweeds removed mods, along with setting the graphics down to their lowest settings(no shadows, etc) and the game runs fairly well on my system. I still get some occasional lag on Lonesome Road and Dead Money, but most of it is when there is a shitload of action going on(LR, for example, in the tunnles after leaving hopeville, and SM after starting the opning gala, when there are a lot of the Ghost People showing up) - about 15 seconds or so each time, but clears up once the amount of "actors" onscreen die off. But other than that, the game runs pretty smoothly. Try the three remover mods I suggested. Just one thing to note - if you start a new game with them active, it will cause you to NOT be able to draw your weapon, so start with them off, make your character, save and quit, then reload with them active. If you still have lag, start turning your graphics settings for the game to a lower setting. Even on the lowest settings, it still looks pretty good, at least in my opinion. Other than that, there are other performance tweak-type mods avaliable here on Nexus - I've never used them, but some of them duplicate the effects of others, so check up on them if you need to do more tweaking.