<<Boost is totally and utterly irrelevant so whoever told you that doesnt understand the principles of tuning a YB>> I know that its all about cylinder pressure, temp (PV=nRT ...) (I am an industrial chemist / comp sci guy).
I have learnt to adapt to what people are comfortable with. I did not mention that I am looking at a GT30R turbo which reportedly pushes more volume of air at lower pressure than comparable T4 .... But elected not to confuse the question. As you asked about the turbo This turbo may be innefficient at higher pressures (30psi) and not able to achieve the desired hp (540 at engine) its sweet spot is high CFM at lower pressures / temps. I have looked at some alternatives but would like to find something between GT30R and GT35R but have not found it. Do you know of something that fits the bill there ?
I am also looking at cams, compression ratio, porting... as you indicated its more than just pressure... Currently looking at CR around 8.5, mild porting , no change in valves and medium cam with GT30R... if you have a suggestion on this I am very interested...

I have found that many people seem to find it easier to talk in terms of boost pressure than CFM... I don't want to start a war on who knows what...

A lot depends on the use of the car, to hit high boost (wring its neck ) every so often is easier on the gasket than hard charging around the track on a regular basis.
It is in the back of my mind to just stick with what I have currently as suggested and run the higher boost as suggested. The guy who initially built the engine recommended not to, so I am trying to abide by his advise.
I will be doing track days and some road use, I just don't want the car damaged in the future and thinking, I could have prevented this, it may be that there is a workable solution at reasonable cost that I have not encountered.

I appreciate all of your feedback guys...