Has anyone experienced any HP gains or real benefits to upgrading the stock air filter to the K&
#11
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No seat of the pants differences that I noticed. I had one in my 1.8T A4 also, which I yanked at the same time as the S4 one. The A4 definitely had more turbo whistle with the K&N filter installed.
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Too many opinions and too many methods. Some say drill 1 hole, some drill 8 holes, some connect a pipe. I have no idea now what I'm supposed to do. LOL.