I want to share my experience and, hopefully, help you with your problem. For a long time, I also faced the fact that sites loaded incredibly slowly due to domain blocking via pfblockerNG together with my local Pi-hole DNS servers. And, frankly speaking, I was already starting to think that I would have to put up with this forever. But after a little experimentation, I managed to significantly speed up page loading! The solution turned out to be simple, but brilliant - configure pfblockerNG and Pi-hole so that they return "empty" responses instead of waiting for a timeout. Thanks to this, the browser stopped constantly trying to load blocked domains, and the network speed increased noticeably. What is especially nice is that this solution worked on all devices in my network, including mobile phones and tablets, without the need to install any extensions for Firefox or Chrome. As a result, my system works smoothly: Squid caches, SSL is filtered, ClamAV checks, and sites open instantly. Setting this up was a bit of a pain, but the results exceeded all expectations - finally a feeling of complete control and stability of the network!