Huh? As I said before, I recall an auto magazine dyno test for a '94 Integra LS. Power barely went up (maybe 1%) starting about 5000 RPM and barely went down (maybe 1%) at 3000 RPM or lower. I recall the one thing about a K&N I noticed was that it didn't muffle the sound of air flowing through the airbox. I "recharged" my filter once, and I was worried about whether I was under/overoiling it. I trust the oiled paper Subaru OEM filters to protect my engine better than any K&N.
I think a K&N may make sense for someone interested in racing, as part of several cumulative mods. However - electronic engine controls just won't take advantage of more airflow short of running at wide open throttle.
For me, the best solution is the one in my '95 Acura Integra GS-R. It uses a larger cylindrical paper element with a two-stage intake runner system. At lower RPMs, the runner restricts air intake to improve low-end power/driveability. At 5500 RPM, it opens up so that the engine can breathe deeper when it needs more air. Another solution is one that Subaru has already thought of, called a "turbocharger".
As for other stuff - the oil companies have no incentive to go out of their way to improve mileage or emissions. They could include fuel stabilizers to increase the shelf-life of their product, but don't because it costs money. Carmakers face punitive action if their CAFE numbers don't meet requirements.