Air filter K&N or Wix

I've used it in a few of my cars, and have noticed a very slight (~1-2mpg) increase in mileage. Power, eh, if there's any I can't feel it...

I had installed a K&N air filter and noticed a good increase in power and fuel economy.

K&N's work great, just don't over oil them. I've been running them for years on all my cars. No problem with the Touareg either in 10K miles.

The only thing im using is a KN Drop-In Filter and that's it.

basically the dirtier a paper filter gets the less it flows...not true for K&N

the paper filter is better for maybe the first 500 miles, after that the K&N breathes better and does not lose its air flow/filtration over time

I had my k&n installed on my passat at 19k miles, i have had no problems but was warned when i purchased it to not put too much oil on it when you clean it as to not @!#@! up the MAF. I haven't noticed a performance gain with the K&N, however when the stock one was put back in i noticed how quiet my engine was when reving hard. I don't like it at all so im putting in another k&n(i like the noise)

I have had a K&N in my 1999 Passat for over 20,000 miles. No CEL's or any other problems. I didn't notice any siginificant performance gains, possibly a 1 mpg increase in gas mileage. To be safe, I haven't put a K&N in my 2001.

The only effect you should notice is larger chunks of debris getting into your engine. This may cause some more noise.

One problem that you can have with the K&N over the stock air filter is over-oiling by novice users. If you over-oil it and the extra oil gets onto the mass air flow sensor, you will need to replace the sensor. Supposedly they aren't cheap either. K&N filters can also be a pain to take care of too. When they get dirty, you have to wash them and re-oil them. This adds another time to screw up.