Until Valve make it a little easier for people to join steam group servers we are using search keys so when you search for a server via a lobby it will try to use our dedicated server first (for all game types).

To enable this feature right click on your Left4Dead2 game in steam and select 'Properties' then select launch options and add the following line:

+sv_search_key "tempestpeons"

Automatically when you search for a dedicated server it will try and use ours first.