I've seen quite a few people say the same thing supporting K&N. I've also seen people make those claims about TB spacers, "tornados", fuel line magnets and other products. But I've never seen it backed up by any objective test. EVERY objective test I've seen by any other source invariably shows no significant improvements, and usually worse performance in some categories (like bypass particulate for foam filters). That includes the above referenced test along with magazines and the like. I've also seen side-by-side mileage tests and dyno results with NO appreciable changes in performance when comparing like to like (new to new and so on). Often times the reported gains (although clearly not in your stated gains) are simply the effect of replacing an old used filter with a new one, and a clean Delco would have produced the same results.
And yes I do believe what I read in that article. I was following along on TDP while the test was going on. Those numbers were provided by a solid, reputable, and unbelievably accurate lab that stakes their reputation and business on providing accurate data for tests like this. The manufacturers were all asked to provided contradictory evidence, if they could. To my knowledge, not one manufacturer has provided any data to contradict the tests in that article. If the article were false, I don't believe K&N, UNI or others would allow that miss-information to be spread for long, do you? If it were unfounded, I would expect at the very least a lawyer's letter to the hosting sites insisting on it being removed.
Frankly, I agree completely with the statement that most of the K&N (and similar) purchases are misguided and driven by marketing hype. IMO, based on every piece of objective information I've ever seen, is that foam elements have their place, but that place is not increased power (in the typical application) or fuel mileage. It does well in wet environments, and if used/cleaned properly, may eventually save money in some cases (but not likely given initial cost, cost of quality oil, and the time/trouble invested in cleaning and disposing of waste). But unless you use it in wet environments, I wouldn't run foam. I am replacing my DMax UNI filter with a Delco (should have already) and all my off-road trucks that run in a desert environment run paper only…