A couple things come to mind when you bring up that issue.
Firstly, I'd open Task Manager while playing and see if anything is running causing the game to lose FPS dramatically. It's definitely possible something is clogging up your CPU usage and could affect APB due to it being a very CPU intensive game.
Secondly I'd use a different program to monitor your CPU temperatures. Not because the one you're using is unreliable but it's always good to get a different sample from multiple sources. I've had this issue before and it ended up being my CPU cooler that was failing; causing it to throttle so it didn't melt. Considering you said you formatted your PC to try and fix this issue I'd say it could definitely be a hardware failure.
Additionally, you could run your PC through some CPU tests with CineBench or other stressing software to see if it is a hardware issue.
Hope this helps.