So I’ve got 3500 miles on my duramax, I know it’s not even broke in yet. When I first got the truck while driving especially pulling a load all I could hear is the purr of the engine and a little tire noise. At about 2800 miles when giving it throttle or pulling a load the engine exhaust is more pronounced, not a tic or rumble I can just hear it now. Like a exhaust hum in the cab, has anyone else’s noticed this change?