Wow, that's not what I expected from an "integration". I'm sorry to hear that. Just giving vBulletin the ability to make comments in Vivvo does not seem very useful to me.
Tell me this, then: If I were to use an iframe, and stripped the header and footer from vBulletin, would it appear like it was inside the Vivvo frame and function correctly? Of course, I understand vBulletin has separate controls which would remain, but the header and footer are easily removed. I would be looking to keep the left side nav menu active in Vivvo, and just have a headerless/footerless vBulletin running in the body are of Vivvo.