AFM, ICV, blown head gasket, vacuum leak, TB gasket, running rich, running lean, timing problem, stuffed cas.....
Or
...... take it to a Gtr specialist and get a pre- purchase inspection. If the seller refuses walk away.
Before you take the bolts out you can try with a dremel with an extension, polishing head and some metal polish and see how you go. If no good then yes you can take a couple of bolts off at a time. You can always check the torque with a manual torque wrench when you take them off. Then use the dremel to polish it.
Its a prick of a job but well worth it.
So you bought everything except the coolant hoses and manifold. Is that right? And the turbo was selected for your 26 and I assume it has a .84 rear, is that correct?
In general engine builders won't change all the hoses, sure they inspect them and make a recommendation if they are substandard, but unless the customer requests it they won't change them.
Take it in on Monday. If its a coolant leak then they will note it on a pressure test and then you have to find it (PITA), do a comp test and they will see if its the head/ gasket, if it's neither then as suggested the head might be lifting. I know its a pain in the ass but shit happens. Our cars aren't factory anymore and little shitty things like this happen often. Relax till Monday.
Ha ha the best thing you have ever written.
Seriously though, rbs are a prick to find water leaks. Check all the little hoses around the engine. I had a similar problem for ages and I thought the worsed and it ended up being the joiner near the clutch master cylinder, only saw it because I was under the car and noticed drip stains on the bell housing. Hopefully its just something like that. Usually if its head related the engine start to sound different.
She loves lag.... Nice slow to start with, take your time admiring the beauty..... Just waiting in anticipation for the rush to blow her mind..... That's what I am talking about brother.
You response lovers are always in a rush that's the problem.