I've found the problem: The .mbnk_pc file must be repackaged in soundboot.vpp_pc, and can't just be placed in the saints row the third folder. If any of you know how to used gibbed's tools, you can repackage soundboot yourself and replace the one in the packfiles/pc/cache folder. (Make sure you back it up first!) For the rest of you, I'll have an updated guide hopefully by the end of the weekend.