Many games, including, I think GTAV depend on a fast master core for performance.
Your FX-8350 has a single thread passmark rating of 1504.
Were you to change out to a FX-9590, the single thread rating would be 1720.
A FX-9590 is essentially a well binned FX-8350 that has a factory overclock to the max, approaching 4.7-5.0.
It requires a very good motherboard.
You would be better off trying to overclock your FX-8350 if you had a good motherboard.
What exactly is your motherboard?
Here is some info on what is good or not:
http://www.tomshardware.com/forum/id-2383150/motherboard-tier-list.html
Few games are going to use more than 2-3 cores.
Do not be mislead if you see all 8 threads showing activity in windows task manager.
That is simply windows distributing activity across all available threads.