I like your first paragraph because i think its true There is more technical learning on sau then any other forum, and with such a large amount of good members it makes a great place to be apart of.
Ok, timing;
Im not to expeirenced with engine timing but i know that you shouldnt be focusing on timing to make your power. Realistically the lower the timing the safer its making the given power. Now also, the fuel you are using is fairly low RON, 95 is only a few RON off normal unleaded. In japan the minimum any descent turbo skyline is run at is 100RON. So use BP Ultimate or Shell Optimax which are 98.
The burning properties of the fuel you are using on boost, is directly related to amount of pinging/missing from the engine on boost.
Also, the standard turbo, which many of us know , doesnt really do much after about 11-12psi. The difference in power from 12 to 14 is minimal.
165kw isnt bad considering the setup altho it probably should be making a little more, just remember, certain dynos may read 165, another mite be 175, which of the latter could be correct.
It could be alot of things though, faulty coils at high RPM, some kind of induction/piping leak, a faulty sensor etc