Vacuum line near carbs

Hey everyone, I just finally brought home my new 79 kz1000 e1 a few days ago. Jumped on for a ride yesterday and heard air sucking somewhere under the seat. Found this loose vacuum line. Any ideas where it might go before I tear my tank off trying to find it? I'm a terrible mechanic and am hoping to use this bike to learn a bit but I'll need some help along the way
*edit* sorry for the sideways photos, not sure what happened there

looks like it goes to the petcock.
Steve

To either the petcock or the clean air system.

Thanks for the input guys. Ill run out and take a look at the petcock after i eat. Would it make any difference if i said that the vacuum line is on the opposite side of the bike from the petcock? Also, the bike runs, t a bit rougher than it should. When I cover the vacuum line with my finger, the idle smooths out but not quite all the way

The usual location for the vacuum petcock is located on carb #3 (as you sit on the bike the carbs are from left to right 1,2,3,4. If it is from the clean air system they usually attach to the carb holders 1 and 4 but could be attached to any of the carb holders.

The rubber intake manifolds between the carbs and cylinder head all have a vacuum port. 1 and 4 point down and out and have a cap on them. 2 and 3 point up and in, and this is where vacuum hose hook to, then go to a tee, then up to the clean air system. Also one carb has a vacuum port that goes to the petcock. So either the hose has come of the nipple on the 2 or 3 intake manifold or off the petcock. Most likely off the 2 or 3 manifold.