My advise to you is to get to know someone who is a succesful port guy and be his apprentice for a while before you attempt this by yourself. its little more complicated the way the metal has to be cut for best air flow.
i have whitnessed this from my own port guy...
you can hurt performance more then help it if you cut it the wrong way
just my take on it.
Brian
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Bjuice..
"I'M YOUR HUCKLEBERRY ! "