vacuum line, heater controls help!

line, heater, core, connects, figure, supposed, vaccume, manifold, see/feel, find, diagram, haynes, switch, idea, on/off, valve, mount, putting, dash, entire, controls, back, vacuum, pedal, top/side, pokes, vacuume, frunk

ok, i took apart my entire dash and had it all out, and now im putting it back in. theres a vacuume line that pokes through from the frunk, right over the gas pedal mount, near the top/side of the heater core box... that line, best i can figure, is supposed to have a vaccume on it (from the manifold?) i cant see/feel where it connects to, nor do i have any idea. without it, the heater core on/off valve wont switch, so id like to have it! cant find a diagram in the bgb or haynes...