I'm able to see new posts in a particular forum as a js or rss response by using a url like:
http://sitename.com/external.php?type=js&forumids=123&lastpost=1
Are there additional parameters for paging results? I could not see mention of this in the documentation. VBulletin version is 3.6.8
I found what I was looking for here:
Maximum External Records This option limits the maximum amount of records that can be returned by the external data provider. By default 15 records will be returned. This option allows the user to tack on &count=X to their RSS feed to retrieve more records.