1994 Chevy Beretta hesitation on the throttle

1994 Chevy Beretta mileage: 127,000. I have taken my Beretta to three different mechanics to have this problem solved and have yet to get it lined out. It has extreme hesitation on the throttle, and when the car slows from normal driving speed to a stop it dies. The idle does run rough whereas before this problem occurred it purred like a kitten. I've replaced the computer, map sensor, throttle position sensor, starter relay, and according to the Chevy Dealer they are not getting any new readouts of problems. I'm running out of options on this problem. I'm hoping you may have an idea of what to do.