Exhaust could clunk if something is loose and you have a glow plug out. Just because they are new does not mean one might not be disfunctioning. If it runs unevenly for a minute or so on startup and smokes blue then smooths out that probably is it.

Tom W

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.