I Have three main settings on my r33, 8psi - 10psi - 12psi - 15.5psi, Dont use the 15 much but it is real easy to get it thanks to the high flow exhaust, high flow intercooler, Greddy intake manifold, power fc and Gizzmo boost controller
its heaps easy to get 15psi outta the stock turbo and the response is silly, almost no lag at all LOL
The reliability of the turbo at 15psi is about as much as the lag, Its yet to let go on me atm thou