It is possible that your MAF could become contaminated which could alter the air/fuel mixture. Improper mixtures have been known to cause expensive damage such as cracked pistons from detonation (lean) and melted cats from unburned fuel (rich). I would never use a K&N in my car...

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280