topic locked, so my questions are here:

1. why are we replacing this "plug"? It would seem that it is part # 26 (gasket), in the diagram, that is the failed component allowing "blow-by" of oil and pressure, which is causing the failure of the cover gasket in certain spots.

2. why not replace #26 with a crush washer, re-install original "plug" with copper colored sealer and re-intall new cover gasket and torque to specs?

3. The original post is a bit vague (I've read it 3 times); what additional parts should be replaced/purchased at the same time as this "plug"? gaskets? o-rings? bolts? washers?

One of the guys here machines the plug and cuts a groove for an o ring.  I don't think there's anything to buy other than sealer. Some have used RTV from the local auto parts house, but, the book calls for
a different kind. I'm glad I spent the money. I went to a little independent bike shop and got what their mechanics used. IIRC it was called Three Bond. Never got hArd in the tube, like RTV, that one little tube put the head cover on three times, and I think I used some when I had a Raptor bored out. Used on other stuff, besides bikes, too.
There is no gasket up there. The cam bearings Are the head and cover. I'm pretty sure they bolt the head and cover together and finish the cam hole.. so, you want a thin even application. Then slowly, gently,patiently start making passes, pulling the cover down on the head. Feel of the bolts, don't just go cranking on them. I've heard how cheap and soft the bolts are, maybe someone got some cheaper and softer than mine, but mine survived it being removed and replaced three times, never rounded or stripped anything.
And leave that
Retorque the head bolts
alone. That's just an invitation to an Expensive and troublesome moment.

DesertRat wrote on 09/26/15 at 08:58:59:

I don't think I can explain this to you on a saturday morn without a percussive adjustment.  

it's dry as a bone here:

it looks to be just below the exhaust head:

verslagen1 wrote on 09/26/15 at 09:33:38:

---

---

---

I didn't notice that until you spotted the 2 washers. The head does have a noticeable gap difference front to back. I can see gasket material toward the back (intake), but almost mating surfaces (no gasket material) showing in the front (exhaust).

*arrrrrggggghhhhhh  

leak is from the head bolt, front (exhaust):

Some get away with simply removing the nut.... degrease, dry and seal with high temp rtv or engine sealant....
Make sure to coat the threads too!  Hey, if you have to redo the head, might as well try this first... might let you finish the season.