Every IC engine ( even Mercedes ) is designed ( read that tuned ) to operate into a certain about of back pressure provided by the exhaust system. A common assumption is that reducing the back pressure and allowing the engine to "breathe" more freely will increase performance. This is not always what happens. You may end up de-tuning the system and lowering the performance. I've no actual experience with Mercedes engines, but I do know that their exhaust is already highly tuned as stock. I do have experience on American performance and racing cars and I've seen the dynanometer tests results which show that the proper amount of back pressure increases HP. I wouldn't argue that replacing a plugged cat with a pipe is better than a plugged cat. But I think you ought to post the ? in the performance catagory and see if there is any advice there.

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