Sputters backfires

So I have changed, wires, plugs, rotor, cap, MAP, IAC, TPS, ECM, all new electrical under hood, fuel pump and filter because their both one unit, alternator, air temperature sensor, and yet it still sputters when it is cold or hot, but not all the time. It can start up and ruin fit a good four hours and then mess up or mess up right away and then run fine later but the back fire dies cine out of intake. I am stumped. Please help, thanks.