There is no "default" anything in Funtoo. You can pick and choose all your applications and through your choice of USE flags can further define what capabilities your various pieces of software are compiled with. Funtoo is the ultimate personalized linux os.
That being said; If you want to install PulseAudio then all you should need to do is add pulseaudio to your USE flags in /etc/portage/make.conf and do an update. That will most likely pull in pulse and its dependencies.
This might also help: https://wiki.gentoo.org/wiki/PulseAudio
