Are the four 10mm nuts that hold the turbo to the exhaust manifold supposed to be the copper coated nuts, like the intake-exhaust manifold nuts?

Mine were not. I used a never-seize compound on them.

Some manifold nuts are solid copper.

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84 300D, 82 Volvo 244Gl Diesel

To my eye, they appear to be stainless steel.

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022