Glad you appreciate our work here
Our mods are pretty fast and light, they should not makes this much difference in page load. But for sure, if you get more visitors using our mods, you'll need a better server some day
50 topic per forum page is of course more work than 25, but if it was previously working nicely, I think the reason is to be searched elsewhere.
The main one could have been, in addition to the eventual Internet access possible issues, the massive redirecting phase, when you switched from the able2know mod to our mods. Usually, SE start a massive crawling when they face massive redirection, like if they want ed to be really sure about them.
Since the zero duplicate as well take care of post duplicate, it make even more redirection.
It usually ends after a week or two.
So it could have been this, didn't you see anything in your server stats ?