GPU usage drops accompanied with frame rate drops

My CPU was overclocked to 5Ghz, I have now lowered it to 4.7Ghz. My GPU is not overclocked. However, I think I figured out the real cause of the issue : I got custom cablemod cables. I unplugged them and reconnected my PSU's stock cables. As soon as I did that, my frame time spikes became much more reasonable and my average FPS increased. I'm going to do some more testing to make sure.