do any intake/exaust mods as of late or anything else that'd make it louder? Turbos do have a tendancy to whine, listen to a diesel. Other then that I'd check oil pressure to the turbo, if it's off then I don't like the ideas of what could be wrong myself. Check this site, it's got a troubleshooter guide to turbos.
http://www.turbotechnics.com/turbo/faults.htm
There are a few things you can do to baby your turbo a bit, a BOV is one (no not one of those loud ass annoying ricer ones, I've heard 1G DSM stock ones are good and hold 23 PSI or so) another free idea is to let it idle a minute or two before you shut the engine down, what this does is prevent the hot shaft of the turbo from being caked with carbon from the oil, if your turbo ends up being bad and the shaft is blue, this is probably what happened! Even so a good turbo should be able to easily push 100K without troubles