Ok so I've used the search feature and found nothing, there is a vaccuum line on the top rear of my motor with a screw in it, my vaccuum diagram shows that it is the line to go to the HVAC but I cant find where to route this hose, does is go into the firewall? It's an 88 iroc z with a 305-350 swap, pics would be greatly appreciated

 

Black plastic hardline comes out of the harness going across the back of the engine bay. Towards the passenger side.

I am dubious that you searched as that is a fairly well-known issue.

 

Ok thanks ill check it out in a few minutes, all could pull up with search was the selector switch making a hissing noise

 

I can't seem to find that line, can you post pictures?