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ok so, i just noticed this a few days ago, when im driving about 50kmh and higher, i hear like a hissing sound and it seems likes its coming from somewhere inside the dashboard? i dunno how to explain the sound but its like, i dunno, close to rubbing papers together?? lol but when i dont drive past 50 it doesnt makes any of that hissing. could it be bad vacuum leak? saying this, cuz when the car is warm, the rpm needle goes up and down a few times( i can hear the intake suckin in air and releasing it) then settles down back to normal (in idle). i thanks for any info...