1. EGR Port. 'Exhaust Gas Recirculation'.
2. A plate sits on top with a Vacuum Diaphragm that opens a closes a Valve that allows Exhaust Gases to Mix-In with, and Dilute and Heat the Fresh-AIR/FUEL Intake Charge.
3. Was suppose to Increase MPG and Reduce Actual Emissions?? And Speed-up 'Cold Morning' Warm-up.
4. You could Tap it with threads and the Chips would just fall into the Exhaust port and get Blown Out, into the Muffler.
5. What I Did....Go to NAPA and purchase a 3/8"- 1/2" 'Cup Plug'. They do exist and look like a Small 'Freeze Plug'.. Get One and Drive it in Solid with a Tight fitting Drift. DONE!! Make sure You Buy it in Steel or Brass, ALL Others Will MELT! I have long since UP-graded to an After Market Aluminum Intake.
6. You could also, cut-off a Length of Steel, Copper, Brass, ROD, and Drive THAT In! NOT Lead! It will Disappear!
7. FYI....The Factory EGR Plates are the First thing to Corrode, Seize and Fail. If it was Your aim to Replace it...a New Plate can be Near Impossible to Locate.
MJ