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Old 01-05-2013, 10:02 PM   #18
F1004fun
Registered User
 
Join Date: Mar 2008
Location: Northern CA
Posts: 170
My Ride: '02 330Ci
I think deadwood83 is correct, the sound you are hearing is coming form your throttle body. The cause is modifying your intake. Your factory airbox is designed to cancel this frequency out but installing a CAI intake or modifying your airbox will allow this noise to escape. I noticed the same noise on my car the minute I installed my first CAI, it was a AFE intake with the metal cover on top. Then I went to the Conforti intake which wasn't as loud but still has a noticeable whistle to it.
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