This probably sounds obvious, but you need to find the hose that has the vacuum leak and replace it. You can buy vacuum hose at almost any auto supply shop for about $1/foot (just make sure that you buy the correct diameter). You might also want to check and see if you will need a few hose clamps (which are also very inexpensive).

96 Contour SE Duratec V6 24-valve 2.5L ATX 108,000 mi. Replaced: crankshaft w/ DMD, EGR valve (clogged), EVR, DPFE, PCV valve, evap emissions hose & tube (cracked), window regulator (broken), LH & RH PCV tubes, UIM gasket (leak), ignition coil