1996 Chevy Suburban

Engine turns over, but will not start. Has had a tune up, replace fuel pump, before all of this, the engine wanted to die, lost power no exceleration, when applying gas peddal, it would back fire, miss, and check engine soon, light came on. Had autozone check the computer and it said oxygen censor right bank 1 was bad, I then replaced it. It ran fine for a day light went off on its own, the next day it ran fine and suddenly, it started doing all of these things again, autozone then checked again and the computer said 2 oxygen censors were bad, one of which I just replaced. Autozone said that it couldnt be the oxygen censors causeing these problems, they reset the code and it has yet to come back on, they believe its something eletrical or fuel, I have since gave it a tune up and replaced the fuel pump and stranier, it ran fine until two days later, I drove it somewhere it ran fine, once I parked and soon returned it will not start again, it just turns over, I have checked the fuses and replaced the fuel pump relay. What else could it be?