Well, it seems that my M5 will not pass emmisions with its current Catalytic converter. The Nitrious Oxide level is double what is allowed here in Pennsylvania. My question is, what are the benifits of replacing the stock CAT with a high-flow cat? Has anyone had any experience with this? Also, any one know of a good aftermarket cat to look at? I plan on replacing much of the exhaust system with its European counterpart at some time in the near future, what does this do to my decision? Any and all advice will be greatly appreciated..................

Have good pricing on DEC cats. Worked great for me.

Mark - Thanks... I called discountconverter.com, they seemed to have a couple of differnet cats for my car. Unfortunatly, they new very little about BMWs.... I think I'm going to stick with an OEM Cat, from what I understand its allready high flow....