I was just taking a look at the Holset website and fond this in the “know your turbo” area. Here’s another reason to put the pedal to the floor after long idles. This one is new to me:

Engine Idle
Avoid running your engine for long periods in idle mode (greater than 20-30 minutes). Under idling conditions, low pressures are generated in the turbocharger which can cause oil mist to leak past seals into the two end housings. Although no real harm is done to the turbocharger, as load is applied temperatures increase and the oil will start to burn off and cause blue smoke emission problems.

http://www.holset.co.uk/flash/index.html

 

Interesting!!

Maybe thats what causes the "SOOT" or "OIL" some people mention having on the intake impellor vanes. It has to come from somewhere.