Using Guide-API-1.10.2-2.0.2-45. If you're holding a Guide book in your hand or you drop it into the world, your fps plummets. We're using Silent Gems and Crossroads which both add a book using GuideAPI. It happens on 4 out 5 of our computers (can't tell on mine, because my monitor holds it steady at 60fps), but it's particularly noticeable on AMD video cards. Easy to test - if you're holding it in your hands, change to another hotkey. If it's lying on the ground, turn away from it and then turn back to it. I've tested this with assorted forge versions ranging from 2005 to 2073.