I need clarification about the exhaust valve purpose and the rattle issue

This week my 330i developed the exhaust rattle that seems to be fairly common on 330s. I searched the archives at every board I could find, and I know that the rattle is caused by the metal valve in the right exhaust tip. What I am unclear on is what this valve actually does. Some say it is to quiet the exhaust note at high RPMs. Others say it is to maintain torque at low RPMs. Which is it, if either? With the engine off or idling, should the valve be open or closed? What would be the consequences if I simply remove the valve, or fix it so that it is permanently open? Thanks for any help or advice.