A dusty/blackish soot coming from exhaust... '89 200

I don't drive my '89 200 much anymore and I notice the other day while hard on the gas a dusty-blackish soot coming out the back... at first I thought it was just dust from the street but then followed the better
half later that day and saw for myself that it was coming out of the exhaust pipe.
It will only do it at high RPM under full throttle (1.4 bar) yet if the engine has been running for a while it doesn't seem to be there. Matter of fact today after a 100 mile run to San Diego, I took off from a toll booth, full throttle up to max RPM (1.4 bar) and it was clean with no visible signs of the soot.... Any idea's on what this could be and where to start?
SO.. I replaced the original rear muffler and catalyst converter about four months ago, the middle muffler is still original (parts were not available and I haven't had time to have that one replaced plus it is still in good condition) and I replaced the O2 sensor late last year. Also sometimes I get a really dusty smell from the exhaust as well as a sulfur smell every so often... it was there before/after the catalyst swap. My thinking is the middle muffler, at 15 years old could that be producing the dusty black soot at higher RPM's?
Oh and earlier this year when it was cold and the car was warming up, it would leave a wet black mark on the concrete that came from the exhaust. it wasn't oil or oily, just black like it was wet soot.
Thanks for any advice as always :)
-- Taylor
'89 Audi 200 '03 Audi S6 Avant '98 Jeep Cherokee Sport
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Taylor, Sounds like you have a pressure leak after the turbo - causing some boost pressure to escape and the engine to run rich. Check the hoses and intercooler caps for leakage. I doubt that the middle muffler would cause the soot you describe - sounds like too much fuel for the amount of air in the cylinders. Cheers! Steve Sears 1987 Audi 5kTQ 1980 Audi 5k 1962 and '64 Auto Union DKW Junior deLuxes (SPAM Blocker NOTE: Remove SHOES to reply)

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On Mon, 25 Aug 2003 09:14:07 -0400, "Steve Sears"

Thanks for the input, Steve. Sound reasonable as the past two years I've been replacing tubes, hoses and other rubber parts after so many years of faithful service.
What do you mean by "intercooler caps" is that the "Michelin Man" Hose? Replaced that about a year and a half ago... I haven't really looked much at the hoses around the turbo so I'll start there, any clues on what to look for?
-- Taylor
'89 Audi 200 '03 Audi S6 Avant '98 Jeep Cherokee Sport
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Taylor, The plastic ends of the intercooler often develop leaks - probably due to pressure spikes when letting off the throttle when at max boost to shift (similar to water hammer in pipes when you shut off the tap). I have heard of people re-sealing the intercooler, try putting a large steel pipe strap around the IC and tightening it (not too tight - you don't want to break the plastic) to hold the end caps on. BTDT last week when I installed QLCC. You might consider checking the oxygen sensor - if it's ok, then try an air/fuel gauge to see when the engine is running on the rich side of stoich. Cheers! Steve Sears 1987 Audi 5kTQ - new and improved.....with a sport interior and QLCC...S5kTQ? 1980 Audi 5k - same ol, same ol. 1962 and '64 Auto Union DKW Junior deLuxes - haven't seen the road this year. argh. (SPAM Blocker NOTE: Remove SHOES to reply)
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On Mon, 25 Aug 2003 09:14:07 -0400, "Steve Sears"

You were right about my '89 200 running to rich... it was big time. No problems with the intercooler/turbo hoses though... just horrible settings. The Honda guy I had better not quit his day job.
This was a while back and I forgot what he said but something about the mixture being more than 10% and harmonic something... whatever it was one hour of labor was all I needed and the 200's idle is wonderful, no more black soot or bad smell(s.)
Thanks for the input!
-- Taylor
'89 Audi 200 '03 Audi S6 Avant '98 Jeep Cherokee Sport
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Taylor, No prob bob. Glad to hear it's running well. Happy new Beer....er.....Year. Cheers! Steve Sears 1987 Audi 5kTQ 1980 Audi 5k 1962 and '64 Auto Union DKW Junior deLuxes (SPAM Blocker NOTE: Remove SHOES to reply)
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