I have a '95 e300 diesel. This is a naturally-aspirated OM606 car.

At low elevations, I never see any visible exhaust when I look in the rear view mirror.

However, on a few occasions, I have driven the car at elevations higher than 7,000 feet. I am alarmed at the large amount of grey/white exhaust I see coming out behind the car. It is very visible. It is especially bad when the engine is cold, but can still be seen after warming up. When cold, the engine also "stutters" a fair amount.

I stopped the car, and left it idling. Walking to the back, I could still see exhaust. I did not detect any odor of oil - just "normal" diesel exhaust smell.

Dropping below 6,000 feet, the problem disappears completely.

Is this normal? If not, does anyone have suggestions on what is causing the problem?

I am a noob w/ diesels. Higher altitude = less air especially for a NA motor. Gray/white smoke usually is unburnt fuel....so it makes sense. HOWEVER... I thought the 'modern' diesels has an altitude compensator to 'lean' the mixture at altitude.

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82 300D....went to MB heaven
90 350 SDL....excercising con rods

I think on a diesel its the ignition timing. You could adjust it when you're high, but you have to re-adjust it when you come down cause I think it will damage the engine. I had a turbo diesel that would run fine when the boost was up but pretty bad when it wasn't. There was a very big difference is engine operation based on boost pressure.

At 10,000 ft with my own air pressure I was the fastest car on the road.

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5 speed '91 190E 2.6 320,000 mi. (new car, fast, smooth as silk six, couldn't find any more Peugeots)
5 speed '85 Peugeot 505 2.5l Turbo Diesel 266,000 mi. (old car, fast for a diesel, had 2 others)
5 speed '01 Jetta V6 (new wifes car, pretty quick)
5 speed '85 Peugeot 505 2.2l Turbo Gas 197,000 mi. (wifes car, faster, sadly gone just short of 200k )
5 speed '83 Yamaha 750 Maxim 14,000 mi. (fastest)
0 speed 4' x 8' 1800 lb Harbor Freight utility trailer (only as fast as what's pulling it)

No it's not normal and it seems like your IP is overfueling the engine. The fault likely lies in the altitude compensating device which is present even on the older diesels. Is your air filter fairly clean?

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

The air filter was replaced a few months ago. It should be clean, but I will check it.

It's a long shot but the egr may also be a factor, if its sticking open or held open too long. Isn't it tied to a computer that senses other engine parameters on this engine?
Still the advise from DieselAddict is what occured to me too, that the ALDA is not functioning properly

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!