It depends what you are talking about. K&N makes 2 versions. One is a high flow version of the stock shaped filter. The other is the "filtercharger" which bolts to the intake once you remove the air box. I have the stock filter. It claims to increase flow by 80%. It seems to make a small difference.
Nick.
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Nick Shumaker
1982 911SC Coupe
nickshu@yahoo.com
PCA -- Rocky Mtn. Region