Not 100% positive but im pretty sure based on the white stuff that you were running pretty lean.
Far as the coolant plug I have no idea. I would check into that. See if there actually a hole there a crack etc..

It has been drilled out and re-threaded. Thats the problem.
It might be fixable, but it might form a larger crack in time. As far as I know, there should only be an oil passage behind one middle bottom stud. There shouldnt be water behind any studs unless its penetrated into the water jacket behind.
Also looks like a different stud than stock. Not sure about the JDM heads, but I dont think that stud is original, which would also point to someone tampering with that hole. Someone may have drilled it out (too deep) and put an oversized stud in. That thread pitch and stud size isnt normal.

Ok. I was thinking the same thing just not that someone drilled it. Its a clean hole. I will assemble the way I found it and move on. Thanks for the help guys guess once I fix this idle surge. Ill be running some seafoam to get rid of that .

I dont know how much bigger than stock it is, but you could install a helicoil if you wanted the stock size in there. I dont think it matters much either way. Hopefully with some sealant on the threads you never have a problem with it. I would check as much as you can while your in there, who knows what else the previous owner could have done.

Ide recommend just putting permatex high temp thread sealer on that stud and the other stud that goes into the oil journal. Just re-use that exhaust stud (since its already been changed).
Just be sure to not over-torque that stud. Ide torque the manifold to the minimum torque spec. (18ftlbs)

The end hole that has coolant with the tapered stud, is where some one drilled a bit too deep and went into the coolant jacket of the head.

Goop it up and install again, as long as does not leak you will be fine.

The white on the valves on the exhaust is common enough, just deposits on the valve, you may be a tad lean, or have thin exhaust seats that are not transferring heat from the valve to the seat.

BogusSVO said:

The end hole that has coolant with the tapered stud, is where some one drilled a bit too deep and went into the coolant jacket of the head.

Goop it up and install again, as long as does not leak you will be fine.

The white on the valves on the exhaust is common enough, just deposits on the valve, you may be a tad lean, or have thin exhaust seats that are not transferring heat from the valve to the seat.

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Good info Bogus! The stud on the far right was infact from previous owner drilling to deep and then fabbed up his own fix for it which was a larger drilled/tapped stud that is actually milled down to match the rest of the sizes.

The white on the valves reminds me of the white that you see on the end of sparkplugs when you run to hot, or to lean so I am thinking that the valves are connected with the idle surge the car is getting. We tested the TB with a different IAC and that didn't work so we are working on other options. I am thinking that because the car goes from 500 to 1500rpm up and down up and down constantly at idle and the wideband says 15 to max, 17 to max and so forth.

Productive day, got all new hardware, gaskets nuts, bolts, goop and all and torqued installed and no more leaks! There was no gasket between the O2 housing and hotside which is where the external waistgate had a major leak, fixed three major leaks off the manifold, and one major leak at the downpipe. All that and about 6 broken drill bits, two of them broke off into the head while trying to drill out a stud that broke off inside the head. Managed to use a reverse cut drill bit and get the broken stud out without having to drill and tap the head again. Chased all the bolt threads and everything went back together pretty good. Clearance is really tight on some of the bolts...

Thanks!