Just got my 350z tour back from the body shop after getting hit on the front end. I am noticing major 'growl' inside the car, but outside the car i hear nothing out of the ordinary. Only thing i changed on the car was the stock airbox to the nismo cold air intake. Could this be the culprit? when im accelerating is when it is most apparent, although i do hear it at crankup. with the rpms at or below 2500 its hardly noticible, but the more i get in to it, the louder it gets. Any input would be appreciated.

 

It sounds that the intake is the source. Any intake will increase induction noise, especially at WOT and past 4000 RPM.

 

A vacuum leak in the intake system?

An exhaust leak?