Symptoms that began all of a sudden, when.

Symptoms that began all of a sudden, when engine would warm up to running temp motor would begin sputtering like it was starving for fuel, more so when pressing on gas pedal. Started with fuel filter, did not work, had a mechanic friend look at in in garage and tried several other replacements such as the brain box, EGR, Spider, Intake air temp sensor as well as checked fuel pump pressure and one other sensor that I can't recall its name but is located below left of EGR. Also most times the truck would fire right up but once in a while it would not start at all. I did notice that the temp gauge on dash would sometimes warm up but only to 150 deg, then just suddenly fall off like the gauges were off, sometimes going back up, basically there was a lot of inconsistencies in how the truck would run from one time to the next. It has not been road worthy though since acquiring this problem. My very skilled friend is at a loss as to where to look next. I am by no means as qualified as he. Any Ideas would be greatly appreciated by my vehicle-less mother in law an myself. I have heard Blazers are notorious for these types of problems and particularly the '95 4.3 Liter. When idling it seems "OK" until you put it in gear and put a load on the motor is when the problems seem to worsen. I cant help but suspect fuel delivery issue because when it wont start a shot of fluid will fire up.