As of 0.6.x, ILEditor 2 now includes the ability to search through the contents of IFS directories and source files.
You can right click on either a source file or an IFS directory, select Search and be prompted to search for a string. When the search has finished, a new tab will open with the results. Clicking on the path to the file will open it up in a new tab.
Note: when you search an IFS directory that is very large, it may take some time. A prime example is searching through a directory which might include a directory like