modernwar99 :
I only get around 30fps on max settings and I have a R9 280. Ubisoft ports are known for terrible optimization. Also is your ambient occlusion and anti-aliasing set to off or lowest setting? Also turn off Nvidia god rays if you have them enabled, they cause a good 10 fps performance hit.
30fps max ? I have an r9 280
x and I average 60fps on ultra @ 1080p with exception of god rays(off) and geometry(low).
Geometry is the biggest performance hit with no visual difference at all at 1080p. Try turning it off and you'll get an instant 10fps boost.
Another thing to help increase fps is to play the game in fullscreen mode, with vsync off, but with triple buffering on, beware that everytime you alt tab the game sometimes changes back to borderless, so change it back to fullscreen if you alt tab.
Try changing Terrain to Medium, this can help with fps also.
Also, open the gamerprofile as wordpad and change DisableLoadingMip0="0" to DisableLoadingMip0="1". Also change GPUMaxBufferedFrames="0" to GPUMaxBufferedFrames="3"
Since you have an AMD card, open CCC and create a profile for far cry 4. Change anistropic filterin to override game settings, and change it to x16. Most of the stuttering and fps drops are caused by your GPU rendering new textures and scenary in the distant, hence why you might be experiencing fps drops more often if you're driving a vehicle really fast. Increasing anistropic filtering to x16 in CCC will mean your GPU wont have to render scenery as often, but will inturn theoretically mean a slightly lower average frame rate, but smoother game play. If I'm honest, when using x16, my frame rate average wasn't even impacted.