1990 Chevy Celebrity

I have a 1990 Chevy Celebrity with 90000 miles on it. Coming home from work one day, it shut down on me getting onto the tollway. When I try to accellerate and give it gas, it act as if it's going shut down until I get off of the gas, then it will run. Everytime I try and give it gas and put it under pressure, this happens. I had the plugs and wires change and it still does the same thing. Can anyone please tell me what kind of problem i'm having.

Thank you.