1997 Toyota Corolla faulty acceleration at times

My toyota is having faulty acceleration at low speeds most of the time. I have had the fuel pump, fuel filter, and radiator changed. It also seems to stall between between 50mph and 60mph. At this point, I slowly let off the gas, and pump the gas and this seems to help. I have brought it to multiple car repair centers, and they cannot find the problem for about a year now. At first I thought it was the gas not getting to the engine correctly, but I have been told that the fuel is not the problem. I dont understand why it stalls on me and sometimes at stop signs just completely turns off unless I keep it in neutral and hope that it will go when I am at a stop.