Hey,
One of the shortcuts in XCode is Ctrl+Cmd+up which moves from the .m file to the .h file.
This shortcut always worked well but since I installed TotalFinder, this shortcut opens up a folder in TotalFinder instead of staying inside Xcode for some reason.
You may try to disable individual TotalFinder plugins to pin-point the code causing troubles: cd /Library/ScriptingAdditions/TotalFinder.osax/Contents/Resources/TotalFinder.bundle/Contents/PlugIns
You can move individual plugins out of the folder, then restart Finder.app via CMD+OPT+ESC and launch /Applications/TotalFinder.app again.
I guess the focus stealing is somehow caused by the tabs plugin (that can be disabled via preferences as well).