I've got the same problem. Since the hot fix CPU it's spiking all the time every 30 sec's to 100% and freezes for 3-4 sec. Especially in City's. Jumping from 70% to 100%.
I still have 50 FPS, no drop there.
I fixed the previous one that remained from beta with the "get requested threads" line fix, but now after the patch it's happening again and it's just choking my system to hell.
Half tempted to revert that change to see if it fixes it, but I'm doubting it. I even checked to make sure my edit hadn't been changed.
Now that I look at it, It *did* change. Going to see if setting it back fixes it.