You should try graphing while driving around one of the roundabouts (so you're not streaming in a ton of new city data & textures as you go), and see what happens there.
What I've noticed from experimenting, is that the game will stutter (more like a minor frameskip than full on engine hitch), when new objects are loaded into the game. So driving around in a circle, it will be smooth until a new car is about to pop into view. Then it stutters. You can see this microstutter better if you're looking around while also moving forward, it can be so slight if focused straight ahead that you may not even see it. It's not just when driving, can experiencing it when walking and looking around as well. It's frequent enough that it's really starting to impact my enjoyment of the game. These are pauses that even Gsync can't smooth out.
Entering new "areas" can also trigger a brief blip, but those could just be the auto-saves. I'd have to pay more attention to that next time.
These other pauses are always there, though, definitely not just the auto-saves. Tried everything I could in-game and out to stamp them out. Seems inherent with how the engine streams in content on fly, don't really know more than that. I do know that the game doesn't seem to utilize that much memory, even in the most intense scenes, kinda strange but likely due to console optimizations. Turning on the "Slow HDD" (using an already fast SSD) seems to reduce them as well, but doesn't truly prevent them and also impacts the variety and density of these random objects in the world so not really a fix.