idle problems with warm engine

[badchevy]

I know another members have had similar problems like I'm having but here is what my truck is doing. The truck runs smooth when cold but when warm, that's when the engine starts acting up (it's the same using either tank). It hesitates to take off and sometimes dies when letting off the gas. This is only at light to medium throttle. Everything is good at hard throttle. I already replaced the IAC motor and made sure the EGR valve was working. The TBI has been cleaned and new gaskets installed. I replaced both fuel pumps, one tank w/sender, and fuel filter (truck was not running when I bought it). Also put new cap/rotor and plugs. Truck is an 87 with the 305 engine. Thanks in advance for the help.

[cadillac_al]

Check for codes, that might point you in the right direction.

[badchevy]

Forgot to say, there are no codes present.

[bhuffstutter]

possible vacume leak