Look HERE

 

Look at the huge mufflers! If they each have vacuum valves to cut in the "secondaries", it basically means that two of the muflers are just added weight that slows the acceleration. They might be more useful as ballast to weigh the rear end down for a better front-to-rear weight distribution and compensate a little for the heavier engine. Those outboard mufflers have become decoration and little more.
Am I missing something?

 

Just like the old M5, cut them off and replace with Eisenmann mufflers