1. Open terminal
2. Write something like this according to your project:

3. You will see all files, that contain three20 string.
4. The main thing to make your project compile and start working is to delete three20 entries from project.xcworkspace file, that can be found in finder by right clicking your project file and selecting show package contents. Open this file in any editor(I use Fraise) and using find delete all entries. It is not hard to do this, I had about 3-4 entries there only.
5. Other user interface state files also may contain three20 entries, but they are not important.
6. Also you should delete anything else concerning three20 (files, folders, header search paths, etc.). It’s more simple.