Code p0401 and p0403

[Davy12]

Hi everyone new here got a CLS 350 getting codes p0401 and p0403 related to egr when I start car it hesitates and stalls unplug egr and starts fine and can put plug back on when engine heated up any way I bought a new egr valve and fitted it and the problems still there was wondering if anyone has had this problem before and how to fix any info would be greatly appreciated thanks Davy