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money pits of various forms
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Stoich is not something you need to worry about on a diesel. If it feels good to you I would leave as is.
 
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1995 300D, 1983 300Turbo Diesel, 1980 280 E
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Two cans of lubromoly Diesel Purge

Disconnect fuel line and stick then in a plastic bottle large enough to hold two cans of diesel purge. Start the car and run the engine at various rpm ranges, per the instructions. you will most likely feel 10-20% ( totally guestimated) more power.
I did this on my 1995 e300d and I swear it screached the tires a tiny little bit afterward. It cleans out the injectors big time.
 

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Okay smartass, you forgot (in no particular order) EGR operation (removal), throttle linkage travel, throttle linkage adjustment, fuel pressure (lift pump, check valves and relief valve), injector spray quality (and pop pressure), CCV restriction, manifold leaks (including turbo to intake o-ring seals), fuel tank vent, fuel tank strainer, fan clutch operation, engine temperature (and replacing the sensor if over 10 years old), oil cooler thermostat operation (if oil cooler gets hot), front end alignment, brake drag, vacuum system operation, transmission adjustment, all 3 drivetrain mounts, exhaust system restriction (collapsed muffler/resonator), alternator charging voltage, A/C compressor and clutch operation, tire pressure, differential free play (pinion slack) and THEN adjust the ALDA because you've covered everything thats more likely to cause performance issues.

Did I forget anything?

EDIT: Damn, forgot "check the ball joints".
EDIT 2: jeanmarc109 added the overboost solenoid on the firewall.
Front end alignment
 

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European 1974 350SLC ,'78 300CD& '80 300CD sold , '81 240D SWMBO's Car '84 300CD & Euro
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831 Posts
Always start with the valve adjustment and fuel filter changes then test the clear plastic (prolly yellow or black inside on your car) boost sensing tube leading from the rear of the intake manifold to the over boost valve on the firewall .

All these plus the two banjo bolts often plug up over time and are dead simple to clean out, I use purple degreaser stuff and a thin bit of stiff(ish) wire, the valve is easily cleaned if plugged up, just fill it with the degreaser and allow to soak overnight .

After all this is done hook up a pressure gauge and see how high the boost goes when you're really moving along .

Resist the urge to overboost it .
 

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1984 300D
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5,666 Posts
I did not read all of the posts so this could be a repeat, but I did not see how must boost in psi your turbo is putting out.
If you measure your boost pressure teeing into the ADLA supply line you can tell if the over pressure relay switch is plugged or not.

You might also bypass the over pressure relay switch. If performance improves there is an issue with the switch.

One of the things that is kind of typical is that the wastegate spring gets week over time and opens too soon and your turbo can't produce the same manifold pressure it did in the past. And of course, what condition is your waste gate gat hose in?

If it has an EGR is that working as it should?

Fuel supply issues. Fuel tank screen restricted and or the fuel tank vent all or partially blocked off (frequently by mud).
 
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