Q: Cel on failing smog i get p0400 then after cleaning egr i get p0421, new air filter, cleaned intake rplaced hoses what else can i

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My sub has a p0400 Cel. I cleaned egr valve and replaced hoses after 80 mikes Cel came backbone cleaned 3gr again Cel off after 89 mike Cel back on and p0421 code. I repkaced hoses egr vacumn cleaned intake repkaced air filter ran sea foam thrust gas no white smoke came out. Do i have to replace every part from egr to cat converter. It went smog auto shop that sold it to me refused to smog it I got ripped off put 300 in it so far please help thank you Lorie

My car has 240000 miles.
My car has an automatic transmission.

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