Experts insight needed!-img_20150717_112359-jpgThere is a subtle /slight hissing sound (resembles air leaking or some objects brushing gently against each other) coming from engine bay, when I tap accelerator to reach very slow RPM. I checked the intake pipes , they seem to be fine! I took my car out for a cruise with bunch of friends yesterday , hard-core revving. On my way home, I noticed the sound. any ideas？