I recently bought a 82 300SD and changed out the oil, fuel, and air filters as well as put a new ram air intake. The shut off valve didn't seem to work so I shortened it and re welded it to make it work and pull on the linkage to shut the engine off. Not the smartest idea but it was cheap and I didn't think the part was critical. I'm not sure if I attached it properly but it shuts the engine off when you apply vacuum to it. I also cleaned out the ALDA line and banjo bolt and put it back together. Could I have put the shut off valve in wrong or did shortening it have any impact on the throttle response and could I have incorrectly screwed the bolt and fitting on that alda line as well as the boost pressure anaroid? The car actually ran stronger before all these changes even with a disguisting air filter and clogged oil and fuel filters. The turbo also sounds louder than before but that could be due to the ram intake. This is my first time working on a diesel so bare with me lol.

For starters, rip out that "ram intake" and put your OEM air filtration system back in. You're not doing your engine any favors with that inferior product installed.

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'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.

Why did you downgrade the intake?

There is your power problem. Fix the actuator properly.

The old one used to rattle pretty bad due to weak clamp and eroded plastic but I will try to put it back on.

Sounds like the buffers finally failed, it happens, and replacements are cheap. No plastic there, I think.
If you still have all the old parts, you'll see on the Y looking thing bolted to the block, has a series of holes, the buffers have a stud on either side of a rubber "buffer", one end screws into the hole, the other sticks up through the bottom of the air cleaner housing. Over time they fall apart.

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83 SD

84 CD

You might also have to fix the cause/s of the Engine shaking before the Air Filter Housing rattle can be managed.
It also seems that quite a few folks turn their idle speed way down and that also can increase the Engine shake.

On the Federal 300D there is a thread where you lay a I believe it was 1 inch or 3/4 inch heater hose between the edge of the Air Filter that faces the engine and the Parts below it and this reduces the wiggle room for the Air filter Housing. However, I do not know what the 300SD housing looks like so I do not know if such a thing would work for you. I did the above to mine and it helped.

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84 300D, 82 Volvo 244Gl Diesel

The procedure will be the same with an SD, here's a pic of what I've been using for a long time.
I also have a kit from **************, but this was easier.
That is a square muffler hanger.

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83 SD

84 CD