Found it!!
I dug this up from a BMW Racing Special Interest Group.
I was responsible for evaluating re-usable air filters for a major construction/mining company that had hundreds of vehicles ranging from large earthmovers to pick-up trucks and salesmen's cars. This study was embarked upon due to the fact that we were spending upwards of $30,000 a MONTH on paper air filters. Using them one time then throwing them away. . I inititated the study in that I was convinced that a K&N type filter or oiled foam would save us many dollars per year in filter savings, man hour savings, and of course engines as these would filter dirt better than paper. (yes, I had read the K&N ads and was a believer)
Representative test units were chosen to give us a broad spectrum from cars right through large front end loaders. With each unit we had a long history of oil analysis records so that changes would be trackable. Unfortunately, for me, every single unit having alternative re-usable air cleaners showed an immediate large jump in silicon (dirt) levels with corresponding major increases in wear metals. In one extreme case, a unit with a primary and secondary air cleaner, the secondary (small paper element) clogged before even one day's test run could be completed. This particular unit had a Cummins V-12 engine that had paper/paper one one bank and K&N/paper on the other bank; two completely independent induction systems. The conditions were EXACTLY duplicated for each bank yet the K&N allowed so much dirt to pass through that the small filter became clogged before lunch. The same outcome occured with oiled foams on this unit.
We discontinued the tests on the large pieces almost immediately but continued with service trucks, formen's vehicles, and my own company car. Analysis results continued showing markedly increased wear rates for all the vehicles, mine included. Test concluded, switched back to paper/glass and all vehicles showed reduction back to near original levels of both wear metals and dirt. I continued with the K&N on my company car out of stubborness and at 85,000 miles the Chevy 305 V-8 wheezed its last breath. The top end was sanded badly; bottom end was just fine. End of test.
I must stress that EVERYONE involved in this test was hoping that alternative filters would work as everyone was sick about pulling out a perfectly good $85 air cleaner and throwing 4 of them away each week per machine... So, I strongly suggest that depending upon an individual's long term plan for their vehicles they simply run an oil analysis at least once to see that the K&N or whatever alternative air filter is indeed working IN THAT APPLICATION... It depends on a person's priorities.
If you want performance then indeed the K&N is the way to go but at what cost??? And no, I do not work for a paper or glass air filter manufacturing company nor do I have any affiliation with anything directly or indirectly that could benefit George Morrison as a result. .
Here's the info I have on air filter performance. Tests were done using SAE J726C Test Method 5-best --> 1-worst
A = Oiled foam (AMSOIL, UNI)
B = Paper
C = Oil Bath
D = Oiled Gauze (K&N)
... ... . Filter Type... ... ... . A B C D
Large particle efficiency 5 5 5 4
Small particle efficiency 5 4 1 2
Airflow capacity... ... ... . 5 2 3 5
Dust holding capacity... 4 2 5 2
Load up characteristic. . 4 1 5 1
Backfire characteristic. . 3 2 5 3
Cleanability... ... ... ... ..... 4 1 4 3
As you can see, K&Ns are great for airflow, which is what they were designed for. Their original application was on racing engines, where airflow is important and ultimate engine life was of little concern. They are not as good at filtering as paper or oiled foam types.
Attention: TDR Forum Junkies 
Anyway, I'll keep the K&N for now and check up on the intake/blades during my next service. I've considered the BHAF, but I'd prefer an airbox to keep rain water dripping from the hood/fender area and to channel in cold air. Maybe some of us could take a stroll through the truck section the next time we visit a wrecking yard. Perhaps an oversized airfilter system from a C8. 3 Ford Louisville would work in our Rams. 
