The good news: I can get one which flows better AND is cheaper than stock.
The dilema: The shop suggested a Dyno Max/Walker unit. They claim it flows better, but they have nothing to prove that. Plus, they claim it's lighter. But, they told me they will have to reroute it a little to make it work. They have done other BMW's with dual exhaust tubes before. This is for $430 installed.
OR, I can go with a DEC cat from ALLBMWPARTS.com. The web site gives some build specs, and claims it flows 10% better. This cat is $545, before tax, shipping, and install. I do plan on keeping the car, so quality is a concern.
So, which one??? And, why?