i cant seem to find a diagram either. but any cracks in any lines are not good. pvc related will cause a vac leak.

may want to hit a junk yard and get a new line for that.

try spraying the crack in that broken line. and also move the lines around when spraying them, lift them up, push them down softly. im sure theres more then just the brake booster line. any small plastic lines are vac lines, the rubber ends on them crack.