So the line that comes off the stock intercooler (black with orange stripes) and at the vacuum treee there is a T-connection that goes to the vacuum tree and the other side goes into the firewall, is that the stock boost gauge line?
The black plastic line that goes through the firewall is the boost line.
So what line is that for?
its the line to the boost gauge in the dash, I capped off all of the other lines on the I/C and turbo and had no issues. the only line I kept on the turbo was for the wastegate.
The line you are referring to with the T is most likely for the cruise control.