2002 Ford Mustang GT making a hissing sound when accelerating?

Ok so i don't know much about cars… Ok >.> i know nothing other than the basic stuff a car should know. I have a 2002 Ford Mustang GT and when i cruising it sounds fine but as soon as i push the peddle in just enough to increase speed i get a constant hissing sound from the passengers side of the car, not a friction type hiss but sounds like high pressure air. I guess it sounds like Nitrous from the Need for Speed games if you know what that sounds like, but ofc I'm not using that. Id take it to a mechanic but don't want to waste the cash if its nothing. Any help is appreciated.

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