I had this noise with my 07 seuc. When they did the 0905 enhancement I talked HD into changing the pistons, cylinders and rings also. HD admitted to me the noise is piston slap due to pistons not having much of a skirt. They said it would not affect the longevity of the engine, and it is considered normal. They only agreed to change the additional parts after much discussion and told me the noise would still be there. They did this for customer satisfaction only. After the work was done the noise was gone completely. So I have to say it was indeed piston slap. Ultimately my motor started leaking again after 700 miles at the rear head and mostly at the rear cylinder base o-ring. The dealer also found oil coming into the intake from the front cylinder head. After 3 tear downs they finally decided to give me a new crate engine. I have put about 150 miles on it now (I live in Vegas) and I may be hearing a slight noise when engine is cold only. It is too soon to know for sure. Hopefully this engine turns out to be quiet. It sounds like it is the luck of the draw on these engines as far as this engine noise goes.