I have a 1993 300D 2.5 turbo that had intermittant wastegate opening/closing problems before it finally stopped closing and now the car blows ALOT of BLACK smoke and has no power...feels like it has about 65 hp, like the old 220D. Talked to Dave M and he is not convinced that it is a wastegate problem and suggested that I post the get the "collective" to ruminate on this problem so I can solve it...You guys are AWESOME!!!

Could it perhaps be a clogged cat? Only I reason I suggest that as a possibility is that your symptoms are exactly what I was experiencing recently with my 95 E300D. Disconnected the exhaust, and voila, power was back and smoke was gone. Replaced the cat and everything works perfectly.

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 159k miles
06 E320 CDI "Rutherford", Black on Tan, 178k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 145k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 75k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife