I just bought a used Altima from Carmax. It has 27,000 miles. When accelerating, the car makes a noise that sounds kind of like a sporty throaty sound but at the same time, almost like there is a hole in the muffler. I'm not sure if it's a good or bad sound or if that is what they all sound like or if something is wrong. If anyone could provide details on what the Altima engine is suppose to sound like it would be greatly appreciated.