Pixology

Its a desktop and in vanilla minecraft i get around 30-60fps

Hey guys, Pixology here, I downloaded the Attack Of The B-Team technic pack and I'm getting around 3 fps. The funny thing is when I go into any GUI like the armour menu, creative menu or any machine menu I get around 50fps. Anyone know why i'm experiencing this lag SPECS: http://gyazo.com/6e45b205f2b79ba062cefd10b6423525