That 1st core thing has nothing to do with this. Every n seconds there is a cpu spike, it has nothing to do with overloading cores. I believe it is the game doing some dodgy polling with the usb steering wheel . For me if i unplug my logitech wheel the spike goes away and use xbox controller.......errr but i want to use my wheel. Don't know if it is just happening with logitech wheels, but that is what causes it for me. So yeah just have to live with it, doesn't have a huge impact but it is definitely there.
I was a bit miffed to hear this existed in previous game and yes still have not sorted it.