I could only partly reproduce the lobbylag this morning: Each time I open the lobby from gamesetup it needs some seconds to open. This delay does not occur when using the non-packaged version.
As hinted by @ffffffff calling Engine.GetEngineInfo() seems to be quite costly and caused the delay in my case of "lobby from gamesetup startup delay". This is fixed by caching Engine.GetEngineInfo().mods at init. Should be save to do so as you can only change the enabled mods by restarting the game.