I'm not talking about importing vBulletin's custom user fields as custom user fields on XenForo.
See, you're already importing the contents of the custom user fields inside the 'About You' section of XenForo. My proposal is to not only import the contents of those user fields but also their title, so in the 'About You' section the end result will be:
"$vb_customfield_name" + ":" + "$vb_customfield_contents"
Which will result for example in:
Favorite movies: Inception, Prince of Persia, Avatar, etc.
Instead of:
Inception, Prince of Persia, Avatar, etc.