1996 Plymouth Voyager SE

I have replaced the fuel rail, filter, pump, plugs, coil, wires, fuel injectors, PCM. However, the engine still hestitates when accelerating from idle and going up a hill. The service engine light blinks about 5 times then stops. When driving along at about 30-50 mph the van runs just fine. Also, after stopping when running at 50-60 mph sometimes it will run rough as a cob when idling at stoplight. It does not audibly backfire but the codes have indicated misfiring on the same two cylinders [1 & 5].