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A stumble or stall as the engine winds down to an idle coming to a stop can be caused by a vacuum or exhaust manifold/header leak.
If your cleaning doesn't fix it I would check the usual culprits. The vacuum cap on the intake manifold under the throttle body, the vacuum cap (or hoses if you are CA compliant) on the fuel vapor recovery line at the rear of the valve cover, and your manifold/header bolts.
If none of this or what you have done resolves the problem I would replace the O2 sensor.
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Humm I will check all of these and grateful for all the suggestions. I think I’m going to run it the way it is right now so if it does become “fixed” that way I will know exactly what it is/was.
But if not I will do one at a time of the above suggestions and hopefully narrow it down.
Yet another reason why I enjoy being here so much. The vast breath of knowledge here is incredible particularly for those of us that enjoy picking up a wrench and tinkering ourselves🙂