Since your using Nvidia, I presume you're also using Afterburner in some capacity. Afterburner (amongst others like FRAPS and GPUz) can log component stats at user-defined sampling rate to a .csv for more quantifiable analysis.
Important metrics to log:
- FPS
- GPU usage %
- GPU frequency
- GPU temp
Depending on the results from above you could then look at:
- CPU usage %
- CPU frequency
- CPU temp