vettechjamie

Hello I recently purchased a 2003 gmc sierra 1500 4.8l when i bought it it had a p0300 code. i brought it to a garage and they tested the coils and dont think its that.. they think it was fuel injectors.. cylinders 4 and 6 are misfiring according to the shop.. I replaced all 8 injectors and cleared the code.. been driving it for about 10 miles now and now it occ flashes Check engine light and when the scan tool is put to it it still gives p0300. Where and what should i do next.. current things fixed and changed that ive done to the truck so far. New Starter New battery New evaporator solenoid New Speed Sensor.. Im at a loss as to what can be causing the flashing p0300 code?