Ill try to explain better. Go into the No Limits editor. The sections that you want the 3d tunnels to be on, put the tunnel button on. So they shoul djust have the normal tunnel setting. Then go into the 3d tunnel tool kit and make your desired shape. Once you are done there click on the button with the box with a curved arrow over the top (make 3ds object for track) Then select your track, go through what it tells you to do, and hey presto you shold be all done