check engine light on on 1996 Chevrolet 1500 Pickup

The check engine light came on and took it to Autozone came back with two codes PO300 and P1406. So I replaced the spark plugs and wires. I also cleaned the distributor cap and replaced the rotor and the coils. I then cleaned the EGR value but did not clean the port and replaced it with the same gasket. How can I clean the port holes and with what. Had the codes earse took it for a drive and the light came back on. Check the codes again and they where the same ones. Don't know what to do next, please help. Sam

1 answer
P0300 is random cylinder misfire, P1406 is an EGR related failure which can definitely cause multiply cylinder misfire. Read this article it is very helpful. http://www.engine-light-help.com/egr-valve.html