I did a Carburettor balance and made a larger ( temporary) crossover pipe and all ican say is it made a huge difference. Smooth as silk at idle and cruise. I cannot say how much was due to the balance as they were both done at the same time, but logic says to me that a larger crossover will help to make up for any inequalities.
So the reason for getting another set of manifolds is so that I can compare the two. I am quite prepared to accept that I am wasting my time, but progress is not made by sitting on ones arse.