The VQ is quiet but is it supposed to sound like this?
 

Ive had my Maxima for a few months now and with the warmer weather this is the first time I've gotten to drive it with the windows down. At wide open throttle I can't hear a peep from the engine but I hear this loud sound of air. The car has a K&N filter in the air box and a really cheap replacement to the stock exhaust from the cat back. The exhaust is pretty rusted already and will probably be replaced soon.

Does this sound normally come from the Maxima at WOT? I'm pretty sure it's not the K&N filter because it's not coming from up front but I would think it's an exhaust leak but I can't hear the engine at all. Is this just the sound of a car makes thats muffled really well? or is something wrong because it's not a very pleasing sound to hear when I floor it.

The VQ is pretty loud when the windows are open and you can definitly hear her roar. (which i think is a great...compared to honda and toyota) However, it shouldnt be a muffled sound, and you prob have an exhaust leak. When at WOT it sounds great IMO...you can really hear the engine...not a muffled sound like youre saying.

Either an exhaust leak or a vacuum leak most likely.

Actually, check your intake manifold. If your PVC valve is stuck, it'll suck in your rubber intake gasket. Grab a can of WD-40, turn on your car, and spray around the front and back of where the rubber gasket is. If it's not there, start squirting it over other vaccume lines. If the engine revs when you spray over the part, the engine will rev and you'll have found your leak area. WD-40 is harmless to your engine.

The IM gasket is just behind your front injectors btw... easy check. I had exactly the same problem but mine caused rough idle. It sounds like someoen breathing through their teeth, but 100x louder. :)

There's very little exhaust noise on a stock VQ, mostly intake. Enough to be heard both inside and outside the car..

For a stock car, the engine sounds beautiful, especially when the weather is nice and cool.

Sure does. It's very quiet when under 4k and no throttle though.