i think he just made it more nonrestrictive, plus he has the older non ignition governed one. (valve cover isnt a golden oil color)
i think that he got more top end, possibly more torque from the engine engaging quicker, i have basicly the same thing he has, and they have a surprising amount of torque for there size.
I put a better air filter on, got an exhaust like the one in the video, chopped the canister off and slipped a flexible exhaust over it, drilled out my main jet and adjusted the valves to the correct settings. Yes, you will see an increase in torque.