I have a 93 B2600I 4x4 PU and it does the same thing as your. It gets up to temp then it sputters and then dies. I have been fooling with this for 3 months now. Thinking itis the idle air control valve orthe TPS, or the mass air flow intake. BUT I just found out that it may be the intank fuel pump. For some reason when the engine is cold it is sucking the fuel but when it warms up it relies on the fuel pump. Well, if the pump isnt working then that why the engine dies. I will be testing the pump and maybe dropping my tank if it is the problem and hopefully it will be fixed.
Check it out and dont give up. Also if you have a engine light on, try to get it to auto zone and they will test if for you for free, or you can rent a code reader and do it at your house. GOOD LUCK.