Title says it all. For instance at the very end of the first level when the shutters open up to reveal new york 2.0 my fps drops to like 23, and the moment the cutscene ends and I can look around like normal, the fps rises back up to 30. What could the problem be?

GTX 590, i7 2600k 4.4ghz, 8gb RAM. 1680x1050, all settings at very high except particles (high), shaders (high), and shadows (high). 2xSMAA (MGPU).