Porting/Tapering the Plenum Opening

Items needed:

Remove the throttle body:

Remove rubber intake hose and top of air box from throttle body.
Unplug sensors on side.
Unplug vaccum hose on the top if you have one.
Unscrew nuts on top right and bottom left of tb. (1/2in)
You do not need to remove the throttle cable bracket unless you're replacing the tb.
Remove the gasket.

Remove the hoses from the plenum.
Don't worry about any fuel lines. All these hoses are for air.

Remove the plenum.

Porting:

Use a vice with a towel over it to hold the plenum still, ensuring it doesn't scratch.
Be sure to wear eye protection!
Trace what you need to remove with the gasket.
Using the high speed bit, slowly and lightly begin to remove the metal from the opening.
The high speed bit can take chunks out, so take your time!
You don't want to remove the full 3mm per side required.
Remove about 1-1.5mm of metal straight back.
From there, angle the cut to meet the line drawn with the gasket.
Periodically put the gasket up to the opening to check where the taper needs to meet.
This should take a good hour if you're taking your time.
When you have removed enough metal from the plenum with the high speed metal bit, go back over it with the Aluminum Oxide bit.
This will remove and smooth out any slight gouges and rough spots from the metal bit.

Cleaning up:

Use an air compressor to blow out the metal pieces that fell into the plenum.
While it's off use some throttle body cleaner and spray each port repeatedly until the can is empty.
Before reinstalling the plenum you should also use throttle body cleaner on the lower intake ports, but not a whole can!
Reinstall the plenum, throttle body, and air hoses.