I can tell a difference in the sound of mine in just a few days - it has already mellowed a bit.

You have to drive it like you normally would. I know that sounds silly, but for me at least, the PV2 made me drive a bit differently at first, and the PV2 was closer to obnoxious that way. So for everyone just getting one - you have to not let the noise dictate your driving style - do what you always do rather than alter anything for fear of excessive noise - and it will actually sound better when you do. Not sure I said this right, but other PV owners probably know what I'm trying to say.