This is just sad, but after I start conversion with an NPC - my fps drops to the mid 30s and and never recovers to the back to 60s which it was before the conversion started - in the exact same areas. Reloading a saved games doesn't fix it, but if you exit the game and load the save - bam, back to 60 fps.
I got to thinking and I brought up my inventory and same situation happens. Seems like the UI kills the FPS on dual card setups after it comes up.
Then again, what do i know...