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Did you try looking at the EGR Port down at the exhaust side. There is a small port that can get blocked off. But you obviously have another problem because the EGR does not come on at idle and you said you failed Nox at idle. The only way to produce Nox is by having to much heat in the combustion chamber. This is how EGR works, it introduces exhaust gases (dead air) back into the cylinders to drop Combustion temp., but it only comes on at cruise.
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