please help 94 blazer runs then dies when ran 20 plus mins
 

i have a 94 blazer 4.3 vortex runs good when u can get it to start but after warms up and been running it will start to sputter and lose power then eventualy die wont restart for a few hours if not longer and some times u have to spray some fuel in intake manifold to get to start i have no clue i have replaced the fuel pump wires plugs distributer cap pickup in distributer and still doing same thing i really need to figure this out i have a 5 month old and need to get this thing reliable for my family plesase some one help me

i have also forgot to mention that i took off spark plug wire to check spark and it was yellow insted of blue any clues or any thing to try would be really great i am stumped and losing my mind i drove it to work the other day got there real slow case it started to sputter and lose power let it sit while i was at work had a short day left atfter 4 hours and didnt even make it back home i have no clue what to do