Yes, "crooked" air can lead to decreased hp! LOL!
If you believe that crock, I'd suggest taking a look at the "Tornado" product. You can get it from JC Whitney, I think.
Basically, its an impeller type thing (like a windmill) that you stick in your intake. As the incoming air rushes through, it spins the windmill, not only "straightening" the air, but also giving you a "free" turbocharging effect! All for only $19.99!
The bottom line is this: A normally aspirated engine is only going to use as much air as its head can intake and exhaust through the intake and exhaust valves, and as its pistons can pump in and out of the cylinders. Period. It is not rocket science to develop an intake system that can easily meet the engines air intake requirement (exhaust may be a different story, I am only addressing the intake side).
Sometimes, this is not done by the factory, like in Larry's Corvette example. That example does not surprise me, because nothing GM does surprises me. Such poor engineering on a modern MB, however, would surprise me.
On the other hand, I really don't have anything against K&N, and I actually think in many instances its a good value. Why? Because actual hp increase is not really important, what is important is OWNER PERCEPTION. Therefore, if for whatever reason (either the owner believes the marketing, or thinks he is getting more power because his intake sounds different, whatever) the OWNER THINKS he is getting more power, he will be happy and will be glad he spent the $$. Since most cars are not subject to a stopwatch, reality really doesn't matter, its only the individual owner's perception that matters.