It is the first engine brake I think for Peterbilt and Kenworth, it is made for the interior and exterior.
Installation: open “My Documents” / open folder “American Truck Simulator” / Open Folder “mod” / paste the mod there.
After starting the game and go to edit profile in the top left says a small “management we” icon to click and activate the mod and apply changes and go!
Credits:
TheHDStrelok
