[ngoma]

Hello, welcome to the forum.

One of the failure modes of the vacuum pump is excessive noise (clackey) but the vac pump should not have any effect on power or smoke. The engine can run fine without it. In fact, one of my future plans is to remove it, cover with a block-off plate, and plumb in a suitable electric vac pump and reservoir.

Oil leak that looks like it is from the vac pump could be from the valve cover gasket, head gasket, or the vac pump-to-cylinder head sealing o-ring.

Can you post a photo of the missing plug?

It will take more iterations of troubleshooting to identify the problem area and arrive at a good solution.

Can you describe more clearly the "dramatic increase in sounds?" What kind of sounds?

Tell us about the mechanic. Well experienced in the D24? The crankshaft pulley bolt, camshaft timing, and IP timing are items that require specialized D24 knowledge and tools, not common on other diesel engines.

Verifying the IP timing will tell us much. Also have the turbo checked. Were you able to hear its whine or whistle before? Can you hear it now?

Your answers will determine the next steps...