I acquired my 01' Impala used a year ago. At that time, acceleration was pretty quiet. But with time, the noise is louder and louder when foot on gas pedal. I mean the "normal" revs noise from the front (engine/around). Gas mileage keeps the same. Just the acceleration "sounds" harder and harder. Had the engine checked for a couple of times at regular services, no problem. Catalytic converter is fine.
What could cause this?
Thanks.