Generation IV External Engine - Diy throttle body porting

Hello, any suggestions on "how to" correctly? Necessary precautions?
What grade sanding or stone to use for PORT AND POLISH? If done correctly what kind of gains?
THANKS IN ADVANCE

professionally ported TBs might show a 4-5 difference in HP from everything I have read here. Do not grind near the blade.

Before you take it apart use a sharpie and scribe around were the blade is and use that to know were not to go.