Code P0401 read out?? on 1996 Mercury Sable

replaced the egr valve,the DPFE sensor and the gas cap reset light and still on need help asap..

1 answer 2 comments
Stop replacing parts until you get a complete diagnosis.Was the EGR port cleaned before replacing the valve? Will the engine stall imediately with egr pulled off or does it stumble and try to stay running? If it tries to stay running then you probably have a restriction somewhere that needs to be addressed.
took it to a shop they checked all the air lines no leaks or plugged said nothing wrong but lite came on again
what code(s)?........hello?