Richard - you won't get much of a power boost by just splitting the manifold, but it is the first step to higher power. To get more go you need more flow from the carbs through to the exhaust. To do this you also need more carb (larger or more of them), and a cam with more lift and duration. This gives you better cylinder fill and more power, the split exhaust just lets you dump this larger amount of gas on the exhaust stroke. What you do get right away is the sound...the glorious sound that only a straight six on dual exhaust makes!
cheers,
Ryan
