I might let up the boost a little once I have the front mount and dump pipe on the car, that way in my opinion Ill be pushing the turbo just as hard as I am at the moment, with less restrictions such as full exhaust and front mount intercooler (well at least the piping change) you can safely say that running say 11psi as opposed to 7psi or so with standard gear you'll be pushing the turbo just the same..
As for increase in sound, what sound deadening stuff in the airbox are you talking about? Nothing I could see there? Mine isn't insanely loud, defanatly not as loud as a friends r34 with just a pod filter.. Certainly audible but hard to hear with windows up and a little stereo going.. Its not a whining noise is it?