The firing order on a inline six is 1-5-3-6-2-4. With a split exhaust, there is 240 degrees of crankshaft rotation between each exhaust pulse in the manifolds and pipes. The exhaust pulses in the manifolds go front-rear-front-rear, etc. There's no crowding of exhaust pulses, and plenty of room in each pipe for the flow from individual cylinders. Spliting exhaust on an I-6 actually makes some sense. Dual carburetion is just eye candy unless a great deal of engineering and tuning goes into the process.
Jerry
