I have a 1990 RS 305 TBI that I bought a couple of years ago. I'm trying to get it back to stock condition, all the vacuum lines were blocked off, I found a vacuum diagram and can put most of the lines back in but there is one port behind the throttlebody next to the egr that I have no idea were it goes. Could anyone tell me where it is sup[posed to be connected? I have attached a picture. Thanks..

 

I believe that port is to supply the vacuum reservoir for the HVAC and cruise control. It runs to a check valve, then all the way to the driver side inner fender well where there is a sphere with one vacuum line attached, this is your reservoir. Immediately after the check valve, there is a tee connection which runs to the HVAC controls and cruise control vacuum diaphragm. I have no picture of it, so this is the best I can do...

 

Yeah I just went out and looked at mine that's correct info. there. a big vacuum line feeds to the check valve then it tee's off going to the Heatering/ac system and around the drivers fender for the cruise control or charcoal canister area..

 

Thanks for the quick response now it makes sense...