Was that while playing csgo? Nothing was really busy or hot. If it works, it would be nice to see a graph generated by Intel XTU that includes thermal throttling, CPU utilization and temperatures. Has anything changed since it was working fine? Did you read this thread? https://www.reddit.com/r/GlobalOffensive/comments/1qkzzi/how_i_fixed_my_unusually_low_fps_on_a_gtx_660/
I had a similar system that I gave away (i3-550 overclocked to 3.83 GHz and a 660Ti), but I have no clue how good it runs csgo.