This was the source of some mystery for me. The HPD manual says "Use original oil drain plug and washer to replace the PVC fitting". I had a hard time figuring out what fitting they were talking about. Turns out it is the vent that goes up to the intake runner. The intake runner side gets blocked with a metal plug later in the process. The other side is mid-block above the starter. Remove the nipple and install the old pan's drain plug.

Metal plug installed in the intake runner. Takes lots of heat and tapping with a hammer to get it in there.

EGR blocking plate installed. Nice annodized professional looking pieces.

Now the intake runners can go back on.