The exhaust upgrade does not do much for the noise, it just removes the likelihood of breaking the pipe going to the muffler. Most of my noise cam from a cracked pipe. It helps to duct the air piping from the clutch to the rear of the cab. Both intake and exhaust. Mine runs 5500 rpm at 40 mph. 6000 at 45. The gas mileage was much closer to 25 mph.