I had this same exact problem. On an overrun coming off the highway, my engine would stall at the stop light.

I just cleaned my IAC valve, and this totally helped. ALSO, I upgraded my DISA valve with the o-ring.

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2003 BMW X5 3.0i -- MT5, 3.64s final gears, H&R lowering springs, K-Mac bushing kit
2007 BMW X3 3.0Si -- MT6