What’s my bottleneck?

Lil___

Commendable
Dec 15, 2016
54
0
1,630
Dell XPS 8700 motherboard
10gb DDR3 Ram
1Tb HDD
i7 4790 @ 3.6Ghz
GTX 1060 6Gb
I’ve seen other people play GTA V at 80-100fps with a similar build to mine but I barely hit 40-50 and sometimes dip below 30. What’s wrong?
 

Lil___

Commendable
Dec 15, 2016
54
0
1,630
Ram is at 1600mhz and the pc was prebuilt but I upgraded the gpu, psi, ram, and case. The original computer (A Dell XPS 8700) is fairly new, it isn’t an old motherboard at all, pretty sure it was released in 2014.
 

Lil___

Commendable
Dec 15, 2016
54
0
1,630

Sorry to get back to you so late, and thank you for all your help. I upgraded the motherboard and realized that I was running on 4gb of ram. I apparently blew my 2nd stick.