i have yet to see a k and n do any good on a car. they should be called hot air intakes. drive with you hood open that'll give it more sound and hp

 

Never restrict any motor that has forced induction. Either change your paper air filters consistently ( depending on dirt driving loacations) or stick with a high flow reusable.
One day my turbo got red hot, it was because the filter wasnt flowing enough air putting more strain on my engine. I think the only reason my turbo didnt fry was because i had royal purple oil flowing in my engine. A demanding driver requires performing equipment.

 

With the A6 2.7T 01 I used to have the K&N I put in at 5000 miles was worth doing. It might have been psychological but the miniscule amt of turbo lag disappeared , and highway mileage seemed to improve slightly, throttle response improved too. Roughly $15-$20 for paper filter ( every 7-10000 miles ?? ) vs $50 for a K&N lifetime and you clean it yourself. It pays for itself especially if you keep the car for a while.

 

i just got a stock drop in K&N today. not much power difference, but can hear a slight 'whooshing' sound and also hear turbo spool a little better.