question:

if you are standing in front of the car, and look at the top portion of the intake manifold right behind the fuel pressure regulator, there is an L-shaped vaccum port coming off the manifold. On my 4th gen manifold, there was a largish round thing attached there, but the 5th gen one only the small port. I couldn't see any other function of it then to be a regular vaccum port, but the 4th gen one served some special purpose.

On my 4th gen intake mani, a vaccum line ran from there to the stock intake pipe just before the throttle body - when I got an aftermarket intake, there was no place to run this line, so I left it open. There was no vaccum leak, but I'm not sure what the purpose of that line. Well, I got a new CAI and it has a vaccum port for that line, (it has two - a big one for the breather and a small one for a vaccum line)

what is the purpose of it?? and what is difference in the 5th gen port vs the 4th gen?