Your system specifications for GTA V are: CPU [model], GPU [model], and FPS [value].
Your system specifications for GTA V are: CPU [model], GPU [model], and FPS [value].
I've tested 15.4, 15.5, and 15.6 but seen no change in FPS. I'm using 15.4 now.
Your setup seems a bit unusual. When Vsync is enabled, you get around 30 FPS, while turning it off allows for higher frame rates like 45 to 60 FPS.