The 6.5TD Power Project I put together in 1999 had a pretty raucous rattle when cold and when the hood was up. Part of that was the DSG gear drive, which had some timing advance built-in. The 18:1 pistons may have had an effect too. On the highway though at 65-mph, the rattle was only barely detectable from inside the cab. Sarah's Blazer is like that too... the rattle is only barely detectable at 65-mph.