Poor accleration and quits out of the blue

i got a 2001 ford mustang gt for graduation. it was
sitting in a yard gor 2 years. so far i have put a new
starter, alternator, spark plugs, plug boots, batterry,
fuel filter, fuel pump, and i put fuel cleaner inside
the tank but it still is having the same problem it
wont accleration properly and it quits out of
nowhere when driving.