It sounds like you have a restriction in the EGR system.
Typically high temperature indicates restriction as well as poor idle. Restriction will build up the pressure inside the valve that could lead to deterioration.
Check the EGR tube, good chance there is significant carbon build up and the air flow is restricted.
The EGR tube can be cleaned. Most of the time this will make the EGR system work as its designed to do.
Here is a helpful video:
I have attached diagrams for your reference.
Please let me know of any questions.
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Thursday, September 23rd, 2021 AT 8:20 AM