The US 603.971 doesn't have that. I was wondering if a Euro 140 SD does.

Sixto
87 300D

Nope,no flap on my or any other Euro W140 Diesel I have seen so far .

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Mercedes W140, S350TD, 95.
Mercedes W140, S350, 92.
Porsche 944, 86 N/A.
Porsche 944, 85 N/A automatic.
Porsche 944, 84 N/A.
Porsche 944, 83 N/A.
Opel GT, 73.
Toyota Supra MA61,84.

I FOUND A SOLUTION!
Well not really,like I said I would do,I swapped vacuum operated wastegate actuator,with pressure controlled one.And man all I can say is WOW it is completely different car now .
So my advice for everyone that have vacuum operated wastegate is CHANGE it ASAP .

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Mercedes W140, S350TD, 95.
Mercedes W140, S350, 92.
Porsche 944, 86 N/A.
Porsche 944, 85 N/A automatic.
Porsche 944, 84 N/A.
Porsche 944, 83 N/A.
Opel GT, 73.
Toyota Supra MA61,84.

Like I said, you had some other issue where the EDS computer was limiting boost. But the pressure wastegate is a nice way to bypass the EDS!

-J

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

Yes you were right,but when i checked for boost it was good,maybe it was the dentist sindrome,as soon you get to the dentist office your tooth stops to hurt .

__________________
Mercedes W140, S350TD, 95.
Mercedes W140, S350, 92.
Porsche 944, 86 N/A.
Porsche 944, 85 N/A automatic.
Porsche 944, 84 N/A.
Porsche 944, 83 N/A.
Opel GT, 73.
Toyota Supra MA61,84.