i was looking under the hood today and noticed an emissions hose which is a small black plastic hose with a rubber boot connector at the end that plugs into a check valve from the brake booster, the other end went into a wireloom at the firewall near the distributor, does anyone know what this is actually for and where it actuall leads to?

 

Sounds like the heater/a/c conrol head vacuum supply .
It uses vacuum for vent selections.