[Sluttypatton]

Don't expect any noticable improvement. Really it depends how bottled up your intake is by your air filter. If you have a super restrictive air filter on a high output motor, then it would be plausable for a 15 hp gain from changing the filter. On a regular engine, don't expect anything special. If you are planning on doing any high performance mods to your car in the future I would suggest it, as the more high performance your engine becomes, the more air it will need, causing the stock filter to become more of a bottle neck. The air filter alone won't make a huge difference. Chances are you won't even notice it.

Yes they are different, they use a cotton gauze sandwitched between wire mesh, and soaked with an oil. This oil/gauze combination provides better airflow, while maintaining (or surpassing) the filtering capability of a regular airfilter (which is made of paper).