first off.. its FPS.. not FBS, i thought you had a typo at firstr but then u sid it that way like 2 more times.
2nd... the human eye cant really see over 60 fps,, hell it cant really see (individual frames) over like 30 fps, all it can do beyond that is detect "smoothness" and depending on your monitor you may not even be able to display beyond 60.
3rd... that power supply is way too weak. im surprised u dont frequently bluescreen. with how much power you're drawing
you should have at _least _a 600+ watt PSU, and i would recommend like 700-800
but that wont help your FPS anyways.
and like i said, unless u have a 144 hz monitor your screen cant even display above 60 fps.
so if u are getting frame drops or seeing any sort of difference, it's not your FPS. thats the issue.
if i were to do anything i would first upgrade your PSU to something safer
it wont help this issue.. but it will definitely safe u a LOT of headaches down the line