I'm no expert, but you have my sympathy. Your rig is way better than mine, but my game is running pretty smooth with about 90 mods and having 3 followers. Overheating is my bane. Maybe a memory problem? I think FNV only uses 2gb by default. Try one of those 4gb large address aware apps here on the Nexus. Also Cleanmem seemed to help me out quite a bit http://www.pcwintech.com/cleanmem . You might need the Unified Hud Project by Gopher too. Good luck!