[Zachery]

vBulletin has two choices for cache headers: NONE, zip, zilch, nada, no headers will be sent AT ALL in regards to caching content. That or we EXPLICITLY send a no cache header. Those are the ONLY two options with the software. If ANY other cache headers are being sent, its coming from the webserver and or its configuration. At least, in regards to the HTML content type, which is the output of all normal vBulletin page(s)

You refreshing (forcing your browser to ignore the cache headers) is doing exactly what it should, forcing a check. The reason the site is "responsive" when cache headers are on, is your browser is just grabing the site from its local cache, instead of waiting for webrequests/responses.