I'm not sure about the emmissions thing, that's the first time I've heard that but it's certainly possible. If you look at the inside of the CDV, you'll see it's nothing but a small orifice that slows down the fluid flow. (Most people don't realize you can take the CDV off the car, knock out the orifice and reinstall the CDV in about 20 minutes and it's free and looks totally bone stock...not that I would ever do that...). It's annoying as heck if you are even half-way competent with a manual. I had always heard it was installed shortly after BMW started to offer free maintenace because it prevents the driver from being able to 'dump the clutch' and it tends to protect the drivetrain from serious abuse if a driver is either too hard on it or doesn't know how to drive a stick. BMW figured it was cheaper to change a clutch than the rest of the drivetrain. Be careful though, if you do remove or modify the CDV and then have clutch/transmission/driveline issues...don't count on your warranty to come to the rescue!