holding back when going up hill or hard acceleration

hi all first trouble ive had with the aveo its 2009 model , ive been looking around but cant seem to find my problem , when going up hills the power seems to fall like its holding back the engine management light flashes , if i stop and turn engine off and restart the light goes out and power is back until i go up another incline. ive had it plugged in but no codes are shown but they did notice that on live data the fuel was switching to closed loop fault instead of open loop driving and closed loop dont know if this makes any sense to anyone , hopefully it will any help would be appreciated cheers

it should be in closed loop while driving, this issue is either plugs, the o2 or maf. Since it "resets" itself, i would change the plugs first (the have a short interval, how many miles do you have?)