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      08-26-2012, 05:17 PM   #2
Private First Class

Drives: 2011 335d
Join Date: Jan 2012
Location: Central Jersey

Posts: 189
iTrader: (0)

Somewhat of a guess but it may be a water bypass hose. If a lot of water enters the main air intake because of extreme spashing or high water this secondary air path prevents a high vacuum from being created that could cause the engine to pull the water up into the air filter causing water to be injested, which usually will destroy the engine.