It may very well be the dual mass flywheel if the engine is running rougher at that temperature. Those temperatures can affect the coils, wires and injectors if they are marginal to begin with. This results in the engine running rough and imbalanced which in turn causes the dual mass flywheel to knock. That’s where I would look first. Bearing problems on LT5’s are very rare especially with those low miles. These engines are known to exhibit piston slap when cold however that should go away within a minute or two depending on the temperature. No reason to be too concerned at this point.
H
