Unplayable after upgrading to new PC?

Been playing for a bit and recently got a new PC. Whenever I attempt to play if I'm in the city the game stutters horribly. Even if I'm out in the middle of nowhere if I look at a certain POI it'll start tweaking out. I've tried turning it down to minimum graphics, turning off dynamic meshing, and just about everything I can think of but it is still unplayable. Any advice would be appreciated.