hesitation

first off i have a 94 metro with a 95 engine. heres my situation. when i first start the car it starts great , then when i put it in gear(auto) if i don't two foot it it dies when i start to hit the accelarater. now when i do get it going i have to feather the gas pedal to keep it running at low speed or it will die. now if i put the pedal to the floor it will go into passing gear and accelarate fine. this is all at speeds under 25 mph, now heres the kicker. if i get it on the hiway it acts like it doesn't want to shift right and i have to keep it to the floor until it hits around 55mph+, then it snaps out of it. i can cruise the hiway at 55-70mph and have no problems, even when i come back into town it shifts great at low speeds, no hesitation, for a few then it goes back to hesitation. take it back on the hiway and it comes right back out:banghead: . it is a never ending process. any help would be appreciated.

I am not a mechanic at all but my first guess would be a vacuum leak. That would possibly explain the shifting problem also.