Your state must not test the actual gas coming out of the exhaust. My understanding is that in CA they do (haven't had to do it). The system will not pass an emission test that actually tests the exhaust gas. It may pass a visual and "code" inspection but that's it. I would not advertise that it will pass emissions if I were you. - You are selling a great exhaust system and any system that removes the cats will not pass emissions in most states that test it. You need to remove the cats in order to make decent power gains with the M3. It's not going to hurt your sale to adjust your statement about emissions (and why create an argument with a future buyer?). It's the reality of any exhaust that makes decent power gains on an M3. I just don't want a forum member to buy it and think that they won't have any emissions testing issues... GLWS!
'08 E90 M3 - Alpine White - Sold
'13 E92 M3 - Silverstone II - Sold
'04 E46 M3 - Jet Black - BBS E88, KW Clubsports, Brembo BBK, SuperSprint Exhaust, Recaro