Mine did that and Eric suggested turning the cam sensor in a little more, so that it's not riding on the edge of adjustment. Since I did that ,I have not had any stumbles off idle in 1-1/2 years. Good luck
Tell me if you ever find a cure. On one street coming home every day, I have a place that makes my car go 2-3-2-3-2-3 shifting, if I drive the speed limit. Turbo surge. I have to either coast down the small hill, or give it more gas and accelorate then coast, etc.