Help Galaxy 4G (T-Mobile) stock version help


Hey all,
I have a galaxy 4G that I got at 2.2 and upgraded to 2.3 using the settings upgrade menu. I need to go back to stock, but I don't know what the stock .sbf file is. I cannot root, for this is a company phone and have been given strict instructions not to do so. Anybody out there know the version for the stock 2.2?

Thanks in advance