A 65mm throttle body alows 10% more air over the 60mm, you should have gotten that along time ago. But it will never yield a tenth in the quarter, except maybe on a high-line blower/nitrous/turbo application.
Definetly get it and make sure you get a 67mm EGR spacer or hog your own if it will take it.
One thing, are you still Speed Density?