vaccume line from firewall

i have an 87 jeep 4.0 4x4 and there is a pink vaccume line that come from the firewall and is broken i was wondering if anyone could tell me where it goes too. i dont think it will pass smog if i dont get it fixed and i really need to sell it. please help, thank you

i "think" its for the 4wd either axle or t-case. i dont think emmision vac lines are any color but black.

The pink one on mines goes to the "Heater Valve" on the coolant T fitting. Follow your heater hoses toward the firewall till you find the diaphragm with the hose nipple on it.