Today I've noticed in two different Multiplayer-races that the Smoke und Dust from some cars doesn't disappear. It was there thru the whole race and always there at the same position. I'm not sure if it might be "created" by players that left the Session after that...
Did few laps right exactly after the patch and still, smoke and dust generated once, remain for few laps till the end at some parts of the track.
I hope these files would help you figure this out. I was racing DTM 13-16 @ Moscow and at the end-spiel when smoke was everywhere, sometimes big clouds, my GPU was heating abnormally