Chevrolet Repair: stalling, throttle position sensor, chevrolet z71

Question
my truck starts up fairly well when cold, but when hot at a light it stalls and is difficult to start.  almost to the point of running my battery down. i recently drove it from south mississippi to denver and it rode great.  before i left i changed wires dist. cap and rotor.  thank you for your time. it's a 1991 chevrolet z71 4x4 p/u, 350  throttle body injection  

Answer
Hello Brandon,
Your truck does not use sensor values to determine fuel mixture when it is cold. it uses default values, which may be rich for low rpm's and lean for high rpm's, till it warms up and goes into closed loop.

So once it is warmed up, something is sending an incorrect reading.

A vacuum leak could be the culprit, since it would be air entering the engine that is not being measured.

A sticking EGR valve, PCV valve, intake manifold gasket, leaking vacuum booster, or other leak could do it.
A bad throttle position sensor, O2 sensor, etc could also.

But check for vacuum leaks first. Spraying some carb/PCV valve cleaner around possible leak points can help find it sometimes.

Van