Same here
game purchased on Steam
OS : W10 64 bits
CPU : i5-7400@3Ghz
GPU : GTX 1060 3GB/ last pilot 551.86
8GO RAM
game installed on SSD
borderless window 1920x1080
region : West Europe (France)
Game runs great with low shadows medium/high textures, except the end of each stage (since the start of every last step of the track until the finishing line)
https://youtu.be/E7aIHpY1wIU
you can see in this video that i've no problem with my config most of the time (1080p video very similar to my game experience)
https://www.youtube.com/watch?v=9E5eu-g0LE0
in that one, the fps drop is visible after 01:58, please compare with the precedent video above to see the fps drop at the end of the stage