The simple facts are this...
The inlet tube to the airbox measures 1.5" across, the hose from the airbox to the manifold is a 3" system. If you think that pulling air through that 1.5" is enough to feed your motor, good for you, but its not. The space that the air is pulled from with the stock box is right behind the headlight, which is a very restricted space already. You will see increased temperature at idle, and very low speeds, but moving air is cooler, once again, a fact, otherwise we wouldn't have fans in our houses, cars, etc. And like I said, I'll bet that I pull in cooler air than your stock airbox does, say at 35mph+.
You never answered my questions about your vacuum gauge reading 0 at WOT. And this still isn't the best measure for true flow efficiency because of a large number of other variables.
My filter setup as is, added 2.5 mpg under normal driving conditions and increased throttle response and power. I average ~22 mpg on the highway in my FX4 with 4.10 gears and tires that have a true running diameter of around 29.5 inches. My 95 ford escort saw a 4mpg improvement under mixed driving conditions with the same setup and there was a huge increase, as there is with the ranger, in passing/merging power.
Obviously, if engines came from the factory at full performance potential, like you seem to think, there would be no need for an aftermarket, and of course the auto aftermarket is huge, so, there must be a reason. There are plenty of third party tests that confirm that high flow intakes add power, even without adding a tune. These gains are seen where the motors already flow the best, no matter what engine the intake is put on.
I have been building and racing cars since I was 13 years old, and I know what works at this point and what doesn't. So believe what you want to believe. I'll continue building cars that work and work better than factory. I'll put my ranger to the test, on the dyno, on the track, wherever you need to see the data from, against the stock setup.
For the money, with the cost of what it takes to make HP anymore, its not the best upgrade, and I fully admit that. But it does add power, and overall performance. Decades of hotrodders have proven that factory motors are not made to their full potential, so why would you think the Ford Ranger is any different? Companies make cars for everyone's comfort, not full performance. The make products with planned obsolescence so they can sell you a better product down the line.
This exact same motor produced 210 HP in the mustang and 216 in the Land Rover LR3. Working in the auto industry for a long time, these kinds of differences are made from better flow, not engine tunes. The power differential on a Challenger vs a Charger for example, are a result of different exhaust tuning, otherwise the engines are completely interchangeable.
So, do what you want to do, I'll enjoy my extra power and fuel economy, but most importantly, my throttle response. But please, understand that the MAJORITY of people who have problems with high flow intakes are changing the volume of the the intake tube and not compensating for it. These companies knkow what they are doing, and don't believe for second that they stay in business by selling lies and snake oil K&N has been in business since 1969, companies that don't have a good product don't stick around that long, especially in the economy of today.