Chevrolet Repair: c1500 chevy pickup, vacuum hoses, vacuum leak

Question
we have a 1992 chevy c1500 pickyup, is stalls out, idles fast and misses horribly. sometimes it runs like a brand new one.  Can you help with this problem 4.3 v6

Answer
HI RANDY, THIS IS A TOUGH QUESTION BECAUSE THERE SOUNDS LIKE IT MAY HAVE A FEW ISSUES OR ONLY ONE....LETS TAKE 1 AT A TIME.
IDLES FAST>> COULD BE A VACUUM LEAK,COMMON PLACE TO START WOULD BE THE THROTLE BODY GASKET.
GET YOURSELF SOME CARBURETOR CLEANER AND SPRAY ALL AROUND THE BASE OF THE THROTTLE BODY AND INTAKE MANIFOLD AREA AND ALL VACUUM HOSES.IF THE IDLE COMES DOWN WHERE YOU ARE SPRAYING YOU FOUND THE VACUUM LEAK. REPAIR THIS FIRST. THIS MAY TAKE CARE OF THE STALLING ISSUES AND MISSING PROBLEMS.IF YOU CAN GET YOURSELF A SCAN TOOL AND FIND WHICH CYLINDER IS MISSING THIS WILL HELP, OR PULL OFF ONE IGNITION WIRE AT A TIME TO SEE IF THERE IS NO CHANGE IN THE RPM'S THAT WOULD ALSO TELL YOU WHICH CYLINDER IS SKIPPING. -SO, REMOVE ONE SPARK PLUG WIRE AT THE DIST-CAP AT ONE TIME,WHEN THERE IS NO CHANGE IN RPM DROP YOU FOUND THE ONE CYLINDER THAT IS NOT FIRING. THEN LOOK AT THAT CYLINDER LOCATION AND CK FOR ANY VACUUM LINES AROUND THE INTAKE THAT RUN OFF THAT PORT. I THINK YOU WILL FIND A BIG VACUUM LEAK, WHICH COULD ACCOUNT FOR YOUR ABOVE PROBLEMS.THE FACT THAT THIS COMES AND GOES SOUNDS LIKE A VACUUM LEAK.I HOPE THIS HELPS TOM. IF NOT GET BACK TO ME WITH MORE INFO....