Now, this does sound familiar!

I got a huge cloud of burning soot out of my Volvo TD after topping a long grade outside Lousville, KY at night. I suppose the oily soot in the tailpipe caught fire on the up-grade, but there wasn't really enough air to get it really going, and when I let off the pedal at the top of the grade, there was.

Quite spectacular, the chunks appeared to be 1/2" or so, and bounced down the highway behind me the rest of the way home.

The origin was, I think, a combination of oil from the dying turbo (it locked up the next year) and excessive soot from a sticking EGR valve (on the Volvo, if it sticks open at full throttle, you be HUGE clouds of dense black smoke, very impressive).

I ended up with a new exhaust system, I suspect partially becuase of the fire, but at 180,000 miles, I wasn't too surprised it was bad.

Check your turbo for oil leakage, and disconnect the EGR to help prevent a re-occurance. You may have just had a huge collection of soot in the mufflers.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!