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      02-11-2013, 03:59 PM   #41
M3amigos
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Drives: 2008 Jerez Black E93 6MT
Join Date: Nov 2012
Location: Orlando, FL

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I've used K&N filters in all my cars including my M3. I bought one from Amazon for $68 with free shipping. I too had the older charcoal lined filter and I did notice a small increase in engine sound. The power gains are minimal if any as most have mentioned, but it seems the factory intake design is already very efficient.