possible turbo problem?

[oteps]

After I shut off my truck it sounds like a bearing is still spinning for about 10 seconds. Plus it does it if I rev the engine slightly when sitting still. Could it be the turbo going out? I am new to diesels and turbos. I did take the intake tube off and look at the turbo wheel, it looks ok and did not seem to have any play in it.

The truck is an early 99 f350 350,000 miles. I have had it for a year and put about 8000 miles on it. I dont know any prior maintenance history.

[countryraised]

these turbos have bushings not roller type bearings, spinning just means you have good clearances and oil film, if not then it would drag against the bushing or turbo housing.

[oteps]

It just started making noise about a couple weeks ago and it is getting worse. When it started it would do it when I shut off the truck. Now when in park you can blip the throttle and as the engine idles down you can hear the noise. But I just installed a diy intake/air filter. maybe i can hear it better because of that. It did make the noise before but it only did it when you shut the truck off.