Which is the better air filter, K&N or TRD? I am assuming that "better" will result in more power when driven aggressively and more MPG when driven conservatively This is for a four cyl 2001 (that extra 5% will be apprieciated!)

It's not a matter of whats better...its a matter of ... spending 35 for a K&N or 55 or whatever the TRD filter costs. K&N is the original in cotton gauze filters...the TRD one was manufactured by a company of former K&N Engineering employees who decided to make their own. Now that they have gone under...K&N will be acquiring them. Both filters work exactly the same. The only gain you will get is 1-2mpg and in HP terms...I doubt you will feel any difference. You have a 5S-FE and i'm assuming you have an automatic. A mere filter will not help it go faster since 4cyl Camry autos are slow. go with the K&N.

Well I have added the TRD filter to my 2001 Solara SE 4cyl-auto. I know some difference is made from experience. Basically I added a sport universal muffler....and after the switch I think I lost some low-end. Also, the muffler was extremely loud. With the addition of the TRD filter...I regained alittle of the strength at low end...and the sound dampened a bit...not as whiney. Not saying I gained much at all....but before the filter I could punch the gas to show off the muffler.....and most times didnt have the car push. Now, there is an immediate push in the car if I slam the gas.