Vacuum leak in the A/C system

I just bought a 2002 S10 crewcab LS when using the A/C the air flow goes away when going uphill causing me to think there is a vacuum leak in the hose going to the ducting. Can anybody tell me where the hose comes off of the engine going inside so I can find it?? Thanks for any help.

Every vacuum hose leak I have found was under hood- usually right next to intake plenum- or at a connection- most likely at your vacuum reservoir ball- is it plugged in? look for a dangling black vacuum hose or plastic black line-- I have never had to look insde conduit to find a vacuum leak- they are always very obvious- look for split or dry rotted rubber hose at a vacuum tee or vacuum connection...you'll soon find it.