any one ever encounter this? i havent run my bike for a few weeks , in its down time i put a k&n filter and did the marble mod. today i pulled it out to do an oil change and i could here the faintest little barly noticable vacume sounding whistle. i suppose it might be the pair valve attempting to get air????i did put new header on recently and my first thought was an exhaust leak but i checked all that and found nothing.