i have a cobalt that starts fine and then a few seconds after it starts the short fuel trim spikes to 31% and stays there and long trim stays at -1 and then car sputters and dies any ideas would be appreciated. new fuel pump, tried diferent injectors, multiple different mass airflows, new refurbished computer, new plugs, new fuel filter, new catalytic convertor, new cam solenoids, multiple different map sensors, new headgasket and compression is above 150 across all four cylinders. i havent used new o2 sensors yet they seem to be reading fine any ideas?

 

Changed the Fuel pump and Top (upstream) O2 sensor, runs better but still choppy. O2 drops to 0 after 10 seconds.