I was wondering if you could dual exhaust on a 400ex for increased airflow. It seems possible because the 400ex head pipe starts at two and joins into one. Just a question of curiosity.

 

I thought the same too, but I asked a friend of mine @ Crower Engines and he said the possible
performance gains achieved yould be offset by the fabrication cost and possible weight gain with two exhausts(though it would look pretty cool.) Besides, the DMC exhaust is really two seperate exhaust pipes that dump into a single silencer which in effect is what you were asking about.

 

seems like it would give alot of airflow...