Originally Posted by runnin4melife
Would be interesting to try the stock sprocket and see if it disappears (I know you don't have one now). The only thing I can think of since you have a relatively new chain is that perhaps the cush drive in the new hub is culprit. If it is exceptionally rigid or has too much play it could lead to a slack issue that can compound with a tight spot and creat a rather annoying slap. The only real way to determine this is to change one component at a time.
This could explain the "at all speeds" issue because even at a steady speed the cush drive is bouncing back and forth just do to rotational inertia and friction differences etc... I am not an engineer but have had enough physics (for the inevitable science driven drivel that will undoubtedly appear on this post).
Could be.... The cush drive for the 950 ( Excel billet hub) is tight. I would say a bit tighter than stock. The rubber pieces are a bit smaller, but harder to press in. I will start with the Chain. What is your with of your stock sprox..... ??? I think the Supersprox is a few mm's thinner....