stumbles on hills

92 olds achieva 2.3 or 2.4 (my sister inlaws car) run fine on level road but when you come to a hill it stumbles almost as if was running out of fuel put fuel gauge on it has good fuel pressure pluds areonly a coulple of months old rechecked the gap .035 has new fuel filter on it no codes if you put it to the floor when it stumbles (as if it has a miss) it kicks down and runs fine. not much into gm i work on dodges at a dealer. bad map? it has 5volts on signal side center pin i can get 2.3volts reving engine in park. any help would be greatly appriated.

hey i would not mind a few suggestions on which way to go with this thing