Wiz I am not doubting you,but I have to ask this. Before you took off your cam cover did you wipe under the frame and surrounding areas?,Taking off the cam cover is a little tight and if it is not clean all around,it is really easy to knock dirt in. I never did have dirt around the cam towers etc,but I did find 2 specs of fine dirt at the top of the vent tube. It's a worthwhile question. I am pretty careful when working on stuff and while a speck or two of dirt might inadvertantly get knocked in/on something never would it amount to this much and so localized. The breather tube itself had the dirt in it also.