[ecomodded]

After some more thought, it dawned on me that the 10 degree increase at the the turbo that would increase fuel usage by 0.7% was just that at the turbo.
I am more concerned with fuel usage when not using the turbo.
Means that the turbo's extra hot air after it has been compressed and heated by the turbo will not like to be increased without loss of economy. When cruising and not using the turbo the inlet temperature is cool to cold on most driving conditions and may very well benefit from a warmer intake temp. In the dead of summer, the road baking hot, air being sucked into the intake is hot, being sucked from 6 inches off the hot pavement(my car) it is hotter then one would suspect,my car gets its best mpg during the summer.
Here's a idea Stan, run a hair dryer on high heat and med heat into
your cars intake, say after the air filter, and note any changes to your {if you have one, i don't) fuel economy device with the car at idle.
Piwoslaw or Diesel Dave or anyone else if you have a fuel economy gauge and a hair dryer or as Stan suggested, run a heat safe hose from over your exhaust to your intake and note any differences
for the good or bad by preheating the air.
If I had a gauge I would be doing the test myself.