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Thanks for posting your question
Does the check engine light stay on when the engine is running?
Is there any type of excessive smoke from the exhaust?
Does it seem to have normal power and acceleration?
Thanks for the reply, the knock sensor code can come up because of the rough idle/misfire, the 71 code is insufficient egr gas flow neither code should cause a rough idle uless the egr valve is sticking and staying open at idle when it should be closed. This would cause a real rough idle, almost stall and lots of black smoke from the exhaust so I'm not so sure that this is the real problem. Try tapping the top of the egr valve with a hammer to unstick it while it's idling and see if it clears up. Before replacing the egr valve and modulator valve I would recommend doing a compression test on the engine, leaking valves or headgaskets are not uncommon on this engine.
You're welcome, do you have any other questions for me today about this?
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