If your Server support z-Lib (most of them does it) turn it on. This reduce the traffic by compresing the trasmitted data to the browser. Browsers can decode it. If you see 'junk' after turning it on you server doesnt support it and you must turn it of again or enable it on the server.
Presistent connctions to a database will hold the established connection open for some time. Most hoster doesnt allow this. Its a little bit faster. If you disable it (default) the connection will open and closed every time.
You are correct Zarzal, both options may make the forum a bit faster to the end user, but can add server load as well - you'd have to weigh your options <img src="https://www.ubbcentral.com/boards/images/graemlins/smile.gif" alt="" />