I saved a guy quite a bit of coin by NOT following the above advise. He actually brought me a turbo to install and told the writer he needed it. As I was beginning to take things apart I'd grabbed the front shaft and gave it a wiggle. Nothing out of the ordinary so I stopped there and called him.... that was why he was replacing it. Thought the "loose" shaft was a sign of it failing. There is "good" loose, and obviously "bad" loose on the shaft of these things.

Sometimes a "whine" or "squeal" noise can be boost escaping under load. Easy to give all the boot clamps a little snug on the air charge system. You can even make a tool to fit the front of the turbo and air psi test it yourself (we have a nice tool at the dealer to do this). Of course it's hard to diag not being "one on one" with the truck, but I've also heard more turbo noise when there is an open element or even K&N style filter in place.

fwiw I can probably count on one hand the amount of turbos that I've replaced for "noise" in the 20 years of doing this.