Sodium sulfite also acts as an oxygen scavenger to protect the metol from oxidation. If you mix a metol only developer with borax and no sulfite, it will go bad very quickly. That's why formulas with metol recommend dissolving a pinch of sulfite first before adding the metol.
Thanks for replying - but if I don't need my developer to keep (i.e. I mix it when I need it), does that work - no SS and borax ?