I had the exact same issue, turns out that my air filter housing was not properly sealed.
Check your air filter housing for improper sealing.
Keep your hand on it at various places, then have someone press the pedal. If you feel air being sucked in, that's your culprit.
Seal it off with silicon, or tighten the nuts around it. (Note: don't tighten too much, its all plastic and might get bent out of shape.)
I took my car to 3S too and they were scratching their heads. All I needed to do was tighten the pipe going into the air filtering housing from the throttle body.
Give it a try!
Sent from my GT-I9500