my 88 mustang gt did the same thing so i took it to the dealership and they replaced the distributer, ignition system, etc. the problem continued. i had suspected it was the fuel pump, and had told them but they did not change the fuel pump. so i ended up paying $2000 for those repairs and more, but the car kept quitting when it would run for a while.
i took it to a local shop and they replaced the fuel pump. now it runs completely perfect.
try the fuel pump