Just installed the s-bend system on my grizzly, what a difference[img]i/expressions/face-icon-small-happy.gif[/img]. It is louder but still a nice sound and this machine rocks even better now. I raced a polaris 700 on a 300 foot sand drag and stomped him. He was stock but I still crossed the finish line first. If anyone is looking to buy a system for you grizzly 660 it is worhth it.