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That code 11 is not really a code, that is a System Pass.
The other codes 31 and 34 are related to the EVP signal when the EGR is supposed to be closed. Code 33 indicates the PCM is not sensing any EGR movement at all.
I would start by checking the EVP output signal. See what it is with the valve closed, then apply some vacuum to the EGR and watch the output signal.Verify if it jumps around a lot. That indicates the EVP sensor is probably faulty.
As far as Code 33, check the EVR it may be bad or someone has disconnected the vacuum source to the EGR valve circuit.
The 31,33,34 are also memory codes in this case. Since you're passing KOEO, clear those and make sure you're passing KOER (I doubt it, in this case). Troubleshoot based on those tests until you get a pass code there, then worry about stored memory codes if they continue to pop up.