Unlike American cars, the original exhaust systems on all MB's are EXTREMELY efficient and well matched to the engine application. Therefore, again unlike American cars, there is little or no gain to be had from aftermarket exhaust components.
The reason these systems, as well as any other MB components related to breathing, are so efficient, is that in Germany, cars are taxed based on engine size. This being the case, the manufacturers work toward maximum horsepower from minimum displacement.
Happy New Year,