Cost to replace EGR system on 1997 Toyota 4Runner

Failed CA smog test, NO(PPM) levels were at 512 (MAX) 88 (AVE) and 747 (MEAS) which is what caused it to fail. Is this related to the EGR system? How much can I expect repairs to cost if it is the EGR system? Car runs very well, no knocking, no pinging, no hesitation...no reason to think there is a problem other than the failed smog test! Many thanks for your help! J

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1 answer 1 comment
I would guess it's an EGR problem but no way for me to know what it'll cost without knowing what's wrong.
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Thank you for the response--it turned out to be a faulty Oxygen sensor which wrecked the cat., so I had to replace both those things--and then it passed.