Get a hand vacuum pump, and when the engine is cold, attach it to the EGR valve (plug the EGR vacuum hose), and apply and release vacuum to it several times. Make sure it moves when you do, and make sure it holds vacuum at the same time. After doing this a few times, start it and see if there's a difference. After the idle settles, try applying slight vacuum to the EGR until it starts to stumble. Is this the same stumble it has at cold start-up?
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