Warm Air Intake?
 

That's a first for me. I have heard of making a cold air intake for more horsepower, but am I guessing right that a warm air intake gives less power but better mileage?

It does for some cars...shouldn't hurt in the winter.

The thing is, I've heard of the ECU's on some cars adjusting to compensate, so some cars just return to their normal MPG after a while.

Theoretically, the ECU plus amm or maf plus oxygen sensor should keep it running right about at stoichiometric ratio - the optimum air/fuel ratio. All the time, once it's been warmed up.

However if warmer air/fuel burns better, it should be better to have a warm air intake. Or where the constant inflow of cold winter air drains off engine heat which must continually be replenished from the combustion process - again, a warm air intake should be better.

Would be nice if someone with a ScanGauge or maybe a SuperMID could test this. However I suspect that most warm air intakes don't yank out of a car that easily - and back in either.

My warm air intake is feeding the engine air between about 48-60 degrees, with outside temperatures between 25-45. I'm sorry I don't have any documentation demonstrating that it helps FE. But it seems to be doing well.