[imperium2000]

With the performance gains from a good set of downpipes, why won't BMW Performance offer them(even catted ones)?

What are the primary problems with the use of such downpipes?

[Zeph]

You typically don't see the manufacturer ever offer anything that removes/replaces a catalytic converter. Actually I think it is illegal. Cars are emmission tested and certified before ever being sold. Even the BMW "Performance Exhaust" is really only a catback or axle-back. It keeps all stock catalytic converters in place. Which brings up another issue of how companies throw around the phrase "exhaust system" yet all they change is a muffler and tips.

[stressdoc]

Anything that alters emissions stuff has to be certified/tested, very costly.

One can only hope that good stuff will be available via BMW Motorsport or maybe even with the supersport version.

[SV Concepts III]

+1 BMW has a variety of factors to consider beyond performance- emissions, sound, comfort etc...

[cstavaru]

The only reason aftermarket downpipes work is the higher exhaust gas flow provided by the lack of catalytic converters OR the use of less efficient catalytic converters in terms of emissions. Draw the conclusions...