Your lucky she didnt get to meet Jason Plato ^^that reminds me forgot to text ya back the other day about le mans - Do you know how much it would cost to go in total
Basically say the first set of pipes out of the engine (primaries) collect into a slightly larger secondary and then the two secondarys collect into a larger collector which tapers down to smaller (same sizes as a secondary ? ) so it flows better.
Generally Speaking 4-2-1 broaden the power range and 4-1 Increase top end. But If you get a decently made 4-2-1 with long primaries and tapered collectors then you should get the best of both worlds