There is none. Just flash to a carrier generic rom.
After that, you will need to update the PRL to a Metro one. You will also need to configure the data settings to go through Metro's Proxy. Do a search and you will find it. (Or you can try one of these carrier cabs:
http://forum.xda-developers.com/show...18&postcount=3 )
It's not a super easy process, I've done it a few times and it was more pain than I expected, but it is def possible. I am thinking about flashing my spare Diamond to Metro for the new gf... (but it takes a lot of effort, esp if I have to do ESN magic with Metro...)