On a buddies 2010, he heard a noise and took back to dealership. They went through all kinds of stuff, but finally came down to the "noise reducing sleeves" that are around the valve springs. They are too tight and springs would rub on the sleeves, making the noise. Apparently earlier 5.7's didn't have these ?? Or had more clearance on them ??? Not sure, but check with your dealership . . .

Cheers

Mark