[kimi_fan]

That isn't quite correct if you're talking about the N55. My right pipe NEVER opens up unless you run at wide open throttle...in fact, after a 100 mile highway trip the left could burn you in a milisecond, the right is cold to the touch. On the 335i with an N54 this is true, the right opens after the car starts to warm up. Mine used to "click" open after a few minutes of idle...and the exhaust note would change.

The posts about opening the actuator in the right side work, you can remove it or simply remove the tube and zip tie the flap on the right side open. Cold startup is very loud but goes away after a minute or two.