Here is a visual set of tests on cotton, foam and paper, name brand filter elements.  As you will see, increase flow rate = increase of dirt into the engine:

http://www.bobistheoilguy.com/airfilter/airtest1.htm

I am modifying the above post, today, to add a new link showing a far more definitive test of air filters.  Forget the link posted above.  Go to this one instead:

http://duramax-diesel.com/spicer/index.htm

His test isn't quantitative enough.  Visual comparation of color density may not disclose the amount and size of the particulate caught by the filter.  At least a before and after weight would have clearly determined which filter caught the most.  Color is determined by how much dirt was impacted on the surface.

Is smoke considered dirt? Since he drives the car 6-8K miles per year it took him 5-6 months to complete his testing. Hmmm....

Okay, let's inject a little common sense here.  He's saying that he placed these test samples in the airflow behind the various tested filters, drove an average of 500 miles with each and the samples indicate how much dirt got past the filters.  That would mean that the overwhelming amount of dirt, likely 90+% of the dirt, was caught by the tested filters and this much got thru after only 500 miles.  Are you kidding me?  Let me go pull my filter out of my '04 Yukon that's been sitting in there for 32,000 miles, filtering dust from a long gravel road driven twice a day for the past 3 years, cut it open, lay it out and no section of it would look anything like that.  But according to his test results it should look several times dirtier than his test samples since it has been filtering the overwhelming majority of the dirt for the past 32,000 miles.  Seriously, show me post-test pics of the tested filters as they should be almost pure coal black if this much got through to the test samples.  

So that link says the K&N filters 97% of the dirt.

If this pic below is 3% of the dirt after only 501 miles, I want to see what 97% of the dirt looks like on the tested filter.  


Obviously this dirt occurred in the first portion of the 501 miles.  Because as the 97% of the dirt accumulated on the K&N test filter, it progressively clogged it up letting progressively less air, and dirt, through to the test sample.  

Heck, I don't know.  It may all be legit.  My concern is that the filter business is highly competitive.  Bobistheoilguy is a site that has cultivated industry respect by presenting scientific, credentialed information.  The fact that they'd present unscientific testing is puzzling to me.  That would be like them posting one of my redneck tests!  The fact that www.bobistheoilguy.com is sponsored by a major distributor of wix filters, a line of filters competing with K&N, Baldwin and Amsoil, makes me a little suspicious.  I figure if the sponors' filters didn't perform as well the article likely wouldn't have been linked.  

But this is still what gets me- if that test filter was placed in the entry point of the tube from the airbox to the throttle body, which is what it looks like to me, and it is so absotutely efficient that it can catch all of the 1-3% of dirt passing the test filters, I can't see how the sucker could drive the car.  That matierial would be so restrictive.  Some of the other links you've given look legit but I've got too many issues with what's presented as AnthonyS's tests.   Still, it simply confirms what we know already.  

The question is, in its stock configuration, can an engine benefit by increasing airflow beyond factory original design? The article in the second link I provided suggests that the engineers who designed the filtration system for their engines design it to provide maximum useful airflow.  Why would they deliberately design a system that adversely affected engine efficiency? Increasing airflow does not necessarily mean an engine can take advantage of it.

Remember, I said a factory stock engine.  The first pic you show, has a highly modified engine.  The blower scoop on it would do nothing to increase efficiency on a stock engine.

You also said you can take any engine, improve the intake efficiency and add fuel, and you've got more power.  Again, intake manifold efficiency can be improved but then you wouldn't have a stock engine.  You've changed the design.  Adding more fuel would do nothing unless you changed the stock design of the engine.  Increase jet size on a stock engine and watch that foul the plugs.  But, modify a Savage engine by replacing the muffler with one with less back pressure, then increase jet size, and then you need less air restriction, MAYBE, depending on the air filter design.  Without expensive lab testing (and not just taking it out on the road to see what she will do), you can only guess about that.

Concerning the manufacturer compromising efficiency due to filter design, look at the example Verslagen gives about taking the airbox door off.  He demonstrated that the math shows less restriction.  If less air restriction was something the engineers were concerned about, they could have easily placed some breathing holes in the airbox door.  Any manufacturer can do this or some similar design alteration.

All this reminds me of the story of how great effort was made by an aftermarket manufacturer to offer expensive modified air cleaner assemblies to be used on the Jaguar V-12 engine.  They were supposed to dramatically increase breathing, and they did.  The engineer who was part of the team that designed the stock system tested the new aftermarket units and showed that absolutely nothing was gained. His comment was: Why wouldn't you think we would have designed an air filter system that was efficient to begin with?

Here is the conclusion of the article in the second link I posted:

"Now I am not saying that ALL aftermarket filters are useless. A paper filter does not do well if directly wetted or muddy. It may collapse. This is why many off-road filters are foam. It is a compromise between filtering efficiency and protection from a collapsed filter. Now how many of our trucks collapse their filters from mud and water? However, if a filter is using "better airflow" as their marketing tool, remember this....Does it flow better? At very high airflow volumes, probably. BUT, Our trucks CAN'T flow that much air unless super-modified, so what is the point? The stock filter will flow MORE THAN ENOUGH AIR to give you ALL THE HORSEPOWER the engine has to give. And this remains true until the filter is dirty enough to trip the air filter life indicator. At that point performance will decline somewhat. Replace the filter and get on with it."

So your saying all of us with pod filters paid money and in return got worse performance?  And those that have replaced the stock filter with a K&N, desnorkled and/or removed the accesss door have actually worsened the bike's performance?  I'll have to respectfully disagree with you to a point.  I think the LS650 airbox is a much better design than on most bikes but I think it can be improved upon, especially if you ride a lot at highway speed.    

For comparison, the weak link for my M50 was the tube between the airbox and the throttle body (FI).  It had two 90 degree bends and and two diameter changes along it's path.  That design was necessitated to accommodate looks (gas tank style, airbox location, etc.).  You could get performance gains with a new intake, FI processor and pipes, but the bottleneck was that tube.  

And that is just the problem here, no one knows what difference aftermarket filters will make on any specific engine without expensive, extensive testing.  A pod filter 'might' decrease performance, if thats the only mod you made. But then it may not.  For sure, you have changed the dynamics of air turbulence getting into the carburetor, which is why Smokey Yurnick instructed in his book, "How to Hot Rod Small Block Chevys", to leave the factory air cleaner housing on the engine.  Also, if the pod filter is less restrictive than the factory filter, it will let more dirt in the engine.  My above links demonstrate that.  But you know what...who cares?  I have a cheap cone filter on my Savage and it really sounds nice.  I like to hear that sound.  What difference does it make if its a little more or less efficient?  The bike has plenty of power as is.  You want to have a cheap, ideal set up?  Buy Lancer's jet set and pod filter, put on a used Harley Sportster muffler and for sure get Verslagen's chain tensioner unit, and you will be in great shape.