Hissing Noise From Engine, possibly intake manifold

I have a 99 GP and there is a hissing noise that comes from the intake manifold area, i talked to a man at autozone and he said it could need a new gasket or something , any input?????!

a hissing noise usually indicates a vacuum leak. Check the myriad of hoses connected to the top of the engine, and make sure your MAP sensor is snapped in tight to the top of the PCV valve ( I'm assuming you have a 3.8) Also check the clamps on either side of the MAF between the air filter box and the engine, as they will hiss if they're loose.

Thanks for the advise, turns out it was a leaky egr valve connection, just not tight enough, no noise now