Torrent check is really what you want it will remove any no longer needed files. It can put them into a folder for safe keeping if you like. The method here w

Torrent check is really what you want it will remove any no longer needed files. It can put them into a folder for safe keeping if you like. The method here works as well. You basically run the new torrent over the old files (so you start half way done). Then move the data folder. In the old folder will be any files that are no longer part of the torrent. In the new folder will be only the files for the new torrent.