Originally, I was doing this by connecting with a client, looking up what DNS servers PIA is giving, then manually setting them in pfSense. I found it easier to just maintain the blocklist myself using pfSense under DNS Forwarder (DNS Masquerade block list).
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http://pgl.yoyo.org/adservers/
Doesn't answer your question directly, but maybe DD-WRT has a similar server (though maybe not).