My car's check engines light came on, its a 2.0 duratec. I had it checked then got the following errors po300, po301 and po303. The car is backfireing when im breaking in gear. The engine light is flashing on and off now and then. What could this be? Also I have noticed smoke when the car is flored. The car has new plugs and plug leads also a new coil pack. Im pretty desperate. I have even tried injection cleaner.