Just adding my support to this. Something is definitely up with the latest patch and FPS performance. It's nearly unplayable in large cities.

OS: Windows 8.1 64-bit (6.3, Build 9600) (9600.winblue_gdr.131030-1505)
CPU: AMD Phenom(tm) II X6 1100T Processor (6 CPUs), ~3.3GHz
Memory: 8192MB RAM
GPU: NVIDIA GeForce GTX 660 Ti