As for vBSEO, which is actually a bit more than a plugin I think... it's helps with SEO via more readable URLs and other stuff. There's likely other SEO-helping plugins/hacks, but I've not really bothered with SEO.
I mean an HTTP status code, the 3XX that redirect a browser to a different URL via the Location header. It happens without vBSEO, I've seen it on my forum, but there seems to be twice as many with vBSEO.
Just curious (wanting to learn), what you refer to as 3XX status redirect, do you mean an indirect redirect/load causing memory usage (because of the title preview, which I think is the one called vBSEO (for vBulletin, at least))?
As in, 3XX status redirect is the process of the vBulletin plugin, while SEO is the plugin name?