Sudden drop to sub 60 FPS during play ????

Yes, me too. 

I have a RTX 4090 and after the patch it's not sub 60, it's sub 30, massive chopiness all around.

And indeed only setting Car Reflections to Ultra Low seems to make it better, and it's not exactly great either, same constant stutters as before the patch.

The car reflections setting must have something wrong, that's for sure. 

Try also GroundCover...eats fps