To check for leak you can do "boost leak test".
You can build your own boost leak tester.
http://www.clubralliart.com/showthre...ght=boost+leak
I have been stressing everyone to use torque wrench to spec. because of things like this. Most mechs' doesn't use torque wrench.
how do you know how tight it is? Torque wrench to spec.
The only time I had boost leak when I took my car in for timing chain replacement under warranty @ the dealership, my UICP pop-off on the freeway.
Since i had to go back & make sure all bolt are torque to spec.