96 gmc stumble problem

96 k1500 ex cab 350 after 30 min's after warming up, the truck will start to stumble. fuel preasure good 62 pounds when stumbling,have changed cap,rotor,wires,plugs,pickup coil,ing coil,temp sen,fuel filter, o2's also changed the fuel injection system under upper intake. cannot find the problem can someone help me:banghead:

96 k1500 ex cab 350 after 30 min's after warming up, the truck will start to stumble. fuel preasure good 62 pounds when stumbling,have changed cap,rotor,wires,plugs,pickup coil,ing coil,temp sen,fuel filter, o2's also changed the fuel injection system under upper intake. cannot find the problem can someone help me:banghead:

Does the check engine light come on when its stumbleing?

the check engine light would blink but would not stay on,when i tryed to see if there were a code it would say no codes to read.