saltyreefs

I have had the cel on for couple months now, first thought it was the o2 sensors, but finally had the codes read, and it was the egr valve, so i took the egr off, cleaned it out, cleaned the sensor which had lots of carbon, and basically cleaned it all. but after resetting the battery the cel came back within couple minutes, which seemed odd, cause last time i checked the o2 sensor and reset the battery, but that time the cel came back about 5 hours later( was done couple times),
so would anyone know if the egr valve is completed toast or something simple, and this all came up right after putting in a chevron fuel injector(costco bought), and there was nothing wrong with the car before the fuel injector was put in, the car runs fine. but hate seeing the cel.
also the hose going to the egr from the manifold had no suction at idle, did not rev it and check suction at hose. could that be also the problem?