Thanks for the help guys, I went ahead an pulled relay #k17 and the air injection stopped cycling but the stumble persisted. The IAC is pretty new less that 5k miles new so I'm not ready to say thats it yet. What I did do was disconnect the connector for the switch over valve and it has not happen yet. I'm going to drive the car tonight for a while and I'll see if it happens again. Is it possible for a bad switch over valve to cause these problems?

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1989 560sec with a few mods.