So I'm going to be checking for vacuum leaks on my 99 sedan. I'm tired of it idling like a tractor so I'm going to start with the basics first. There is a black/white little valve thingy in the vacuum line leading to the brake booster. It has 4 ports. 1 leads to intake vacuum, 1 is capped off, 1 leads to the brake booster, and the 4th leads back to the plastic intake tube between the throttle body and air cleaner. When my car is running, there is ALWAYS vacuum at the line that connects in to the plastic intake tube. I thought there was not supposed to be vacuum there all the time. What is correct? How does the little black/white valve actually work?