Just unsubscribe to the content you dont want and it gets removed http://steamcommunity.com/workshop/...browsesort=mostrecent§ion=readytouseitems
And if you want to re-install WITH the subscribed content, you must copy the following files/folders: C:\Program Files (x86)\Steam\steamapps\workshop C:\Program Files (x86)\Steam\steamapps\appmanifest_322330.acf C:\Program Files (x86)\Steam\steamapps\common\rFactor 2 If you only copy the 'rFactor 2' folder and the appmanifest, you'll have to re-download all the workshop content.