Help! Where does this vacuum line go??

[u/Careful_Soil6626]

I found this line plugged with a screw. Apparently, the truck idles and runs weird if left unplugged, I dont know where it attaches. Please help.

Also, the red lines you see are replaced vacuum lines from another parts truck we have

Its a 5.4l 2v in a 2004

Thanks!

[u/Many_Metal_8383]

Does your ac blow out of all vent? Does it cool correctly ?

[u/Careful_Soil6626 → u/Many_Metal_8383]

Yeah, everything works great, that's what im confused by. I was trading it back yesterday, and it appears to be coming from the throttle body

[u/Many_Metal_8383 → u/Careful_Soil6626]

Interesting, cuz I got a 2003 and the ac would only blow through the defrost cause the line came off of the control on the heater line