i have the K&N on my 2.8l quattro a4 and while not having much to compare it to, like it a lot. it added some good tone to the engine and i can tell a difference. i'm also currently trying to get a decent heat shield fabricated for it so i'll keep ya updated if you end up getting one in case you want a heat shield.
the best set up i've found is a stock itg filter from AWE Tuning and fabricating a new air box around it out of stainless or aluminum, any heat resistant light weight material works, and run a flex hose of some type from the stock grill to the intake box.
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