If your turbo turns out to be good then check for vacuum leaks and then the high pressure oil pump. If your high pressure oil pump isn't up to snuff then your injectors won't work right and you'll have no power.

My '03 has 126,000 miles on it and it's been good to me so far.

I would definately find out what all has been done to it. Definately make sure that the head bolts have been replaced with a good high quality stud.