First of all, the "Stage" of the turbo determines what "Stage" it is most potent in the power band. A Stage 1 is for low rpms and so on. So the Stage 1 is not going to hold boost until redline.
Another thing which everyone must watch out for. In order for an engine to have a turbo, it has to be a healthy engine. So before putting ANY turbo on, do things that make the engine itself run easier rather than something that forces it to run faster.
What I am trying to say is, do the engine balance and the port & polish before ANY mod. That is what I do. They may not give a great increase in power, and they are expensive, but they make the engine more responsive, flexible, smoother, higher revving and more capable to make use of boost. I bet if you made the engine more efficient with P&P and/or Engine Balance, you will see the boost hold on closer to redline, and not to mention you will lose all turbo lag.
Even in the tuning section I believe it says to never add a turbo to an untuned engine lest you reap the wrath of turbo lag!!!
