How are you getting 10%?  1667/(142216+1667) = 0.0116 or about 1.16% stales, not 10%.

Edit: Oh, you're talking about SS:.  What do you have scantime set to?  Try setting it to 30.  Also try upgrading to 3.3.1.

Also I see you're using I:20.  What happens when you decrease intensity to 13?