odd sound on startup

05Monsterdmax

New member
May 31, 2011
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http://youtu.be/eUH-W815X0k
When firing it makes an odd swoosh sound I guess u can call it, sounds like alot of air blowby. Pressure tested the intake system by plugging the downpipe and intake, but no leaks. Any ideas? Removed the belt and it's not in the serpentine system. Doesn't always do it but 90%+ of the time it does.