how do you change +or clean the egr?

there is lot more to the egr code, 400 than just replacing the valve. you need to have it checked to verify. there is a lot more than the valve in the egr system 300 is a random missfire 443 is an evap code. Roy

i agree with mastertech. the egr could be causing code po300 but not the evap,seek a proper diag and est as to not waste time and $