deceleration noise.

[Signature620]

Does it have the same noise when you come off of the engine brakes? The detent pockets in the valve rocker shafts wear out and the rockers can have a hard time staying in their neutral position. This allows them to knock back and forth between the cam and the exhaust valve - Creating a top end rattle constant with engine rpm. If this sounds like your issue, you can pull off the rocker cover and try to rock the engine brake rockers by hand to see how solid they lock into their neutral position.