I can help you.
but I am not good at english.
so I am sorry.
anyway,
the solution is that edit your file which path is "/System/Library/CoreServices/Finder.app/Contents/Resources/MyLibraries/myDocum ents.cannedSearch"
for example
I need to search my "data" partition.
it must be mounted in "/Volumes/data"
and do this
==========================
.
.
.
<dict>
<key>FinderFilesOnly</key>
<true/>
<key>RawQuery</key>
<string>(true) && (((kMDItemContentTypeTree = public.content)))</string>
<key>SearchScopes</key>
<array>
<string>~/</string>
<string>-Library</string>
<string>-Music/iTunes</string>
<string>-Documents/Steam Content</string>
<string>~/Library/Mobile Documents</string>
<string>/Volumes/data</string> ############# Import this line #############
</array>
.
.
.
<integer>1396925814</integer>
<key>FXScopeArrayOfPaths</key>
<array>
<string>~/</string>
<string>-Library</string>
<string>-Music/iTunes</string>
<string>-Documents/Steam Content</string>
<string>~/Library/Mobile Documents</string>
<string>/Volumes/data</string>
<string>/Volumes/data</string> ############# Import this line #############
</array>
</dict>
.
.
.
==================================
and you can find what you want to look in you "all my files".
I am sorry that I am not good at english.