Rough idle/no rev problem

[tada]

I did the noid test and found to my dismay that all injectors were pulsing. Not really my dismay, but an end to the quest. But while I was underneath the car wresting to get to the injector plug on cylinder 4, I found the tube shown below unhooked at one end near the driver side front of the engine (maybe the PCV valve?). The other end goes under the plenum and somewhere below or into the manifold (possibly to AOS). Fairly rigid tube, not rubberized. I hooked it back up by feel to what I guess is the PCV on the drivers side crankcase cover near the firewall. I could not see the ends from above or below. So before I get all excited and reassemble everything, can someone tell me what this tube is and could it be causing a vacuum leak? No, I did not see smoke in this area from the smoke machine.

Sorry for the big picture and it's cockeyed angle. I'm referring to that small bend of tubing hiding there above the spark plug hole in the crankcase. Thanks for the help!