This car has performance issues and nothing I have done has improved it dramatically. Could I remove the oxidation catalyst and weld-in 2 straight pipes. Do you think that would help low end power?

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1994 S350D
1995 E300D
1997 E300D

Yes and only if it's clogged.

Can you disconnect the downpipe and go for a drive? It'll be loud and might leave a sooty mess in the engine bay.

Sixto
87 300D