Hi Dennis:

I'll take a whack at this since nobody's responded yet and I posted the exact same question some months ago. A mechanic responded very eloquently about turbos and I can't find his email address. You might be able to go back to see the post in the archives. Was late last fall. He has done a lot of work on turbos.

Anyway, I was told by him that the newer turbos (post about '88) are equipped with a "water jacket" type of apparatus that helps to cool them, which makes prolonged idling prior to shutdown unnecessary. He did say, however, that 1)NEVER, run the turbo hard prior to a normal warmup of the engine and 2) NEVER, shut down immediately after running it hard without a cooldown.

I appreciated his advice, and I am very conservative. So my policy is to take note of how long the engine is idling on the way to the parking spot and include it the one-minute cooldown. If I race into parking I'll sit there and let the engine idle for a minute; if coasting into parking I'll give it considerably less. But I always give it something. It can't hurt. It just makes me feel better to go easy on my turbo.

Hope this helps. I'm sure somebody with a much higher degree of knowledge will respond sooner or later.