When i start my car up under the hood all i hear is a little like puffing sound that is very annoying, do i have a leak in my stock manifold gasket? i only have sri, catback exaust, no headers and no headers money right now, so could i just buy a new gasket to stop the annoying noise?

 

it goes up and down with rpms, right? but if its an exhaust leak, it will just start to sound like crap, not so much a puffing sound.