Possible to use my pfsense router to "clog" my internet connection on purpose?

[ghurty]

I have a cable modem with that support two routers to be hooked up to it.
I have a pfsense router on one and a different one on the other.

I am trying to stress test the internet connection. As i want to see how good voip will perform when the internet is on a full load.

Is there a way that I can run a script or a command on my pfsesne router, so that it will "clog" the internet connection for both?

THanks