[Vanner]

Sorry I don't really know how to bring up them fancy quote boxes, but these are from tjts1:

"On the bmw i was able to to measure the temperature drop from 20-40f above ambient stock down to 0-5f above ambient."

Then we know your cold air works. It should decrease fuel economy for the reasons I listed above. Thanks for clearing up what you were talking about with the factory systems, btw.

"Read the autospeed articles. Its not about pressure, its about reducing restriction. The large forward facing intake improves fuel economy by making the engine a more efficient air pump at low RPM and high load. This will allow you to use 1 or 2 gears higher at any given load."

The exact opposite. At a given rpm, the load will be reduced, which is bad for engine efficiency. I understand it's not intuitive, but you have to realize that throttle plate is more than happy to compensate for any restriction you are able to reduce with a CAI/ram air/magic jelly beans whatever. Except, once again, at WOT. You are probably more efficient at WOT. In the second case, for a given load, the rpm will be reduced, which puts it farther out of the range of the next gear, not closer. Engines don't like lugging.

I hate to sound like I'm ganging up on you here, tj, but jon and garys are right. In your high-altitude example, that engine only produces 30% of its power because its only getting 30% of the mass of air it needs. Assuming the computer could compensate (which it most certainly could not) it would only use 30% of its regular load of fuel. The air/fuel ratio stays the same. Heck with no pumping losses it might even be more efficient. Imagine more on the order of 90% here and you have the concept behind a warm air intake.