In default mode iTrash already find most related files. However, sometimes developers of applications uses not so obvious data file names and most uninstall tools do not find those files.
iTrash uses a Levenshtein Distance search algorithm which can trace down more possible related files.
You can switch to Expert Mode in realtime by turning the switch to ON. iTrash will search again but more thoroughly.
Sometimes it will find more related files but it is recommended to verify if the files are indeed related.