So, in or out of gear I have what sounds like a hissing or whining coming from the engine compartment.. not so audible at idle but apparent mostly when increasing RPMs. For example when maintaining constant speed on the interstate I don't really hear it, however when I give it gas, it becomes audible. I can't really hear it well from under the hood; it's more audible in the cab which makes me think it's something maybe vaccumm closer to the fire wall.. any ideas??

 

I used to have a hissing/whining noise inside the passenger compartment. Turns out it was my wife. Got rid of her, no more noise.

 

^ Hehe, beat me to it, 'cept it was a GF. Last time I dated an actress, whew, too intense.

 

is your airbox sealed right? have you removed the cover recently and not got it back on properly?