Don't feel too bad.. Mine is the same way, and the whole emissions system is hackewd up. I got capped vacuum lines all over the engine compartment, and the car still runs rough... no power either, but that might be because I got severe blowby, and probably need a new engine.
To get back on track, what you might want to do until you find where it goes is go ahead and put a screw or plug of some sort in that vacuum line. It will only be temporary and will get the car running good until you find where the line goes.
Good luck with your car.