I'm using PIA too, and I had to add a third variable to core.conf to get my speeds back to normal:
"enable_incoming_utp": false,
"enable_incoming_tcp": false,
"enable_outgoing_utp": false,
Also adding "enable_outgoing_utp" fixed the speed issue for me.
See the post from "Mushroom" about halfway down: https://www.privateinternetaccess.com/forum/discussion/23112/anyone-having-torrent-slowdowns-please-read-this