You have asked the question I wanted to ask. Fitted one on my last Focus RS just an element change, didn’t notice much if any of a difference. The main benefit for me would be one filter for life as opposed to shelling out £20 every two years.
I fitted my k&n the day after I picked my car up and it made hell of a noise difference as expected and just looks better than the standard one. I fancy it did rev better?
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