Dear,
As far as I know, you could check differences by doing this:
1 - Pick some material "A" with componentes "1" and "2".
2- Run with planning mode 1 and check requirements created for components.
3 - Now change BOM and take out componente "2" and include component "3".
4 - Run again with plannig mode 1: it should keep requirement for component "2" and not generate for componente "3".
5 - Run MD01, this time with planning mode 2: it should erase requirement for component "2" (now out of BOM" and create requirement for component "3" (now IN the BOM).
Please let me know if it works...
Rgds,
Marcio